Mihai Fonoage's Blog

Application Ecosystem for the BlackBerry PlayBook

2011-03-26T15:43:00.000-04:00

According to their press release, RIM has officially announced the ecosystem for applications that will run on the PlayBook tablet. Below is a quote from the release:

BlackBerry PlayBook to support BlackBerry Java and Android apps
Native C/C++ development support added, in addition to HTML5, Flash and AIR support
Support from leading game engines: Ideaworks Labs (AirPlay) and Unity Technologies (Unity 3)
BlackBerry PlayBook becomes a new market opportunity for all the developers who have already created over 25,000 BlackBerry Java apps and more than 200,000 Android apps

The most important part for me, and something that I've been hoping for a long time, is the added support for Android. What RIM was lacking was an application ecosystem. This will not be the case anymore. And it is not only about Android in the end. Moving away from Java ME is the first step (still need it for existing applications). When you can write applications using HTML, Flash, C/C++, Java ME, and Android, you can't go wrong. There is no other ecosystem out there that provides such a diversity.

Basic vs Applied Research - Linear vs Nonlinear Models

2010-11-18T08:56:00.001-05:00

I was reading a review in IEEE Spectrum of Henry Petroski's "The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems", and found several references to the linear model of how research is being conducted in the U.S.:

"Part of the problem, he [Henry Petroski] says, is the linear model of technological progress: Basic research spawns applied research, which in turn fuels technological development. This model is wrong historically, and it undervalues the creative juices of good engineering ... This linear model became ascendant in U.S. science policy after 1945 when Vannevar Bush submitted his famous report, “Science—the Endless Frontier”, which enhanced the prestige (and funding) of basic research at the expense of applied work."

I wrote in one of my previous posts about linearity and nonlinearity in biology, engineering, and financial systems, and how linear models (such as blood vessels in biology, waterfall model in engineering) have a negative impact on the systems where they are applied. The review of the book has the same underlying message, namely how moving away from the linear model of basic research towards the more practical approach of applied research (or development projects) has a greater outcome in terms of engineering advances.

Android Ginerbread adds NFC support

2010-11-17T11:58:00.000-05:00

Listening to the conversation with Eric Schmidt at the Web 2.0 Summit 2010, I was pleasantly surprised that the new Android 2.3 (called "Gingerbread"), will add support for NFC, or Near Field Communication (I heard rumors about this in the past). There are many use cases that I can think of, the major one being using your phone for making payments. I said it in the past that the main reason I think NFC has not been adopted is because there was no major company/platform using it. Now there is.

2010 Gadget Census

2010-10-26T08:51:00.000-04:00

Retrevo's 2010 Gadget Census revealed what gadgets people were using in each state, with the summary of it captured in the image below:

Articulated Naturality Web

2010-09-21T22:08:00.000-04:00

Articulated Naturality Web, or ANW, is what comes after augmented reality, the next level, the next phase if you will. There's a short video posted on engadget (and at the end of this blog post) that shows some of the features of ANW. For me, it's amazing because it fuses sensors, location, internet, image processing, and much more into one technology that gives meaning to the surroundings by means of your smartphone. Imagine sitting outside of an hotel, and looking at the available rooms, how they look inside, prices, and booking information. Blows my mind what we can achieve today with the amount of information and the technology available to us.

QPC - Articulated Naturality Web from Justin Montgomery on Vimeo.

Installing iPhone/iPad application ad-hoc

2010-08-26T08:46:00.002-04:00

At my current job, I had to remotely install some beta versions of the iPad app for some clients, before the app was actually released on iTunes. There are several steps that one has to take in order to achieve that (assuming you have followed some of them that describe creating Certificates, App IDs, etc):

In your iPhone Developer account, go to the iPhone Provisioning Portal, the to Devices, and add the iPad device to the Current Registered Devices section. You have to know the Device UDID (40 characters that can be copied form iTunes when you have the iPad plugged into your computer).
Add the newly created device to the Distribution Provisioning Profile.
On you station, drag-and-drop the distributed provisioning profile into XCode.
Under XCode, change both your app's and your target's build properties to use the new distribution provisioning profile.
Delete the old Entitlements.plist file and create a new one.
Change your settings so that XCode uses Device as the Active SDK, and Distribution as the Active Configuration.
Build your app, then zip the executable.
Export your private key and the developer identity certificate and import them into your client's Keychain (you might also need to export-import the AppleWWDRCA.cer file to your client). Finally, add the iPhone distribution certificate to the Keychain.
Download the new distributed provisioning profile and drag-and-drop it into your customer's iTunes app (either drop it on the iTunes icon, or in the App section).
Un-zip your application and drag-and-drop it into the app section of your customer iTunes (if the Apps section is not visible, go into iTunes -> Preferences and click on the checkbox marked as Apps).
Synchronize iTunes with the iPad to transfer the app from iTunes to your client's iPad.

Hope it's going to help some of you. Enjoy!

Introducing BlackBerry 6

2010-07-22T13:55:00.000-04:00

Smartphone Market Share - Q1 2010

2010-07-04T13:14:00.000-04:00

Smartphone Market Share for Q1 2010 (Source: The Nielsen Company):

RIA frameworks used for deployed applications

2010-07-03T10:07:00.000-04:00

Via Software Developers (SD) Times:

Robots: they re-arrange themselves and officiate a marriage ceremony

2010-05-29T11:09:00.001-04:00

Yukiko Sawada and Takashi Tsubouchi at the University of Tsukuba, Japan, have built a self-configuring conference room, where the tables are robots that re-arrange themselves based on an initial configuration inputed through a User Interface:

And, if we are on the subject of robots, also in Japan, a robot named i-Fairy officiated a marriage ceremony:

Mobile Monday Miami - May 2010

2010-05-04T21:10:00.003-04:00

Yesterday evening I attended my first Mobile Monday Miami meeting. It was a breath of fresh air to meet and connect with people that share the same interest as I do, and are enthusiastic about anything and everything mobile. The topic was "Will The Mobile Web Kill Off The App Store?" The overall conclusion was that whether you develop your app on the mobile browser or natively, it really depends on the uses case you have at hand. Let's look at some pros and cons of both approaches:

Mobile Web

PROS: One app for all platforms (almost). With the adoption of WebKit (iPhone, Android, WebOS, Nokia, and soon RIM) and HTML 5, this could become the cross-platform solution that everyone is searching for.
CONS: Getting access to some low level functionality of the phone is very difficult. Could you query the phone's proximity sensor for example? Not really.

Native

PROS: Full access to the phone's APIs that provide you a way to query its hardware.
CONS: Having to develop one app for each platform. There are cross-platform tools that try to mitigate this issue. I haven't used any of those tools, although I wrote about them, but the comment made by Steve Jobs that the platforms will support the lowest common denominator in terms of features. However, I imagine that you could tweak the tools to take advantage of the features provided by every platform that you target.

Another view of the topic discussed Monday was the benefit of having an App Store in terms of discoverability and distribution, a one stop place. This can never be achieved with a web version.

Overall, fantastic discussions, great turnout, I'll definitely become a regular.

BlackBerry in Top 5 of Worldwide Mobile Phone Bestsellers

2010-04-30T18:02:00.000-04:00

As per wired.com, RIM has replaced Motorola in the top five mobile phone companies worldwide based on Q1 2010 sales, and it's tied with Sony Ericsson for the number 4 spot:

This is not unexpected since when it comes to enterprise and messaging, there is nothing like the BlackBerry. On a side note, Motorola has actually had profit for the first quarter of 2010, earning $69 millions. Go Moto!

Ten Best Chapters of Software Development Books

2010-04-25T18:54:00.001-04:00

I have file on my laptop that contains a huge list of books (mostly software related) that I just don't have the time to read completely, or to read at all (but I do have time to write this blog :)). Beside the list of books, the file has links to other lists of books of the type "every programmer should read", "must read", you got the idea. Dustin Marx came up with his own list, but what is different is that it gives you a list of best chapters of software development books, chapters that he "found to be most influential or most impressive" in his career as a software developer. If you're just like me, you will appreciate the list.

The Marshmallow Challenge

2010-04-24T16:57:00.001-04:00

Tom Wujec conducted a team building experiment called the marshmallow challenge with people ranging from kindergartners to CEOs, with results that were surprising. His presentation is below:

Perfect Mobile Platform

2010-04-12T18:53:00.002-04:00

What would make up the perfect mobile platform? What characteristics should it posses? Here are some of them, in no specific order:

User Interface/Experience - a rich user interface that provides a great user experience. When using the phone, everything should come naturally, with ease, and should have the WOW factor that makes you never want to leave the phone out of your hands. Doing common tasks should not take more than a few clicks.
Application Ecosystem - Having many applications to chose from is not as important as having quality applications, those that satisfy a particular need, like finding a place to eat, checking your email, or playing Doom. Integrating location, social networking, and sensors is a must.
Internet Browsing - surf the Web from anywhere, on the go. A mobile browser should be able to render pages properly and fast, navigation should be done with ease, data should be compressed as to save bandwidth, and use the latest web technologies (HTML5, CSS, JavaScript, etc).
Battery Life - it better not leave me hanging after a full day of use, or in the middle of a call, or while searching for a place to eat using the GPS.
Development Ecosystem - provide a rich set of APIs that can access all the features of the phone, and can provide the best user experience. Provide tools that can be used to make it easier to write apps. Publishing an application should not involve much hassle.
Openness - here I refer to not only an open and free platform, but to a platform that allows any mobile technology to work on it.
Enterprise - features such as security, integration with email/calendar/notes/contacts servers, messaging, to name just a few.

There is no one platform that satisfies all these needs better than any other platform. What is needed is a platform that has the user experience of iPhone and Android, the application ecosystem of iPhone (and Android very soon), the internet browsing of iPhone and Android (mostly any WebKit-based browsers), the battery life of the Blackberry, the development ecosystem of Android and iPhone, the openness of Android, and the enterprise characteristics of Blackberry.

Will we ever have such a platform? I really doubt it.

Smartphone Application Downloads Forecast

2010-04-08T11:23:00.002-04:00

ABI Research has recently published a forecast for smartphone application downloads world wide for 2009 - 2015, and which can bee seen in the chart below:

While iPhone apps are still going to be the leading source of downloads, for the year of 2010, Android is expected to have over 800 millions application downloaded, a major increase compared to 2009. Beside iPhone and Android, Blackberry and Symbian are also catching up on sales. What all this means, at least for me, is that it is a great time to be a mobile developer :)

We will live in a game

2010-04-05T18:51:00.001-04:00

"We will live in a game!" This is what you will take away after watching Jesse Schell's presentation at DICE 2010 summit. He envisions a day that has normal activities, like brushing your teeth, eating cereals, watch TV, etc, but which will let you win points and benefits when attending to those activities.

Great fun to watch the presentation, very intriguing and eye opening at the same time. Read about it via IEEE Spectrum.

Battery Information using iPhone's Cocoa Touch

2010-03-03T22:35:00.002-05:00

I have done something similar (although on a smaller scale) to this but for the Android platform. For the iPhone platform, the main class used is UIDevice. Below is the header used:

#import <UIKit/UIKit.h>


@interface BatteryInformationViewController : UIViewController {
    IBOutlet UITextView *batteryLevel;
    IBOutlet UITextView *chargingState;
    // Used to format the battery level
    NSNumberFormatter *numberFormatter; 
}

@property (nonatomic, retain) UITextView *batteryLevel;
@property (nonatomic, retain) UITextView *chargingState;
@property (nonatomic, retain, readonly) NSNumberFormatter *numberFormatter;

@end

There are two UI elements (text views), namely the battery level and the battery charging state. The corresponding implementation file is next:

#import "BatteryInformationViewController.h"

@interface BatteryInformationViewController ()

- (void)displayBatteryLevel;
- (void)displayBatteryStatus;

@end

@implementation BatteryInformationViewController

@synthesize batteryLevel, chargingState;


- (NSNumberFormatter *)numberFormatter
{
    if (numberFormatter == nil)
    {
        // Used for formatting the battery level
        numberFormatter = [[NSNumberFormatter alloc] init];
        [numberFormatter setNumberStyle:NSNumberFormatterPercentStyle];
        [numberFormatter setMaximumFractionDigits:1];
    }
    return numberFormatter;
}

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Register for battery level and state change notifications.
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(batteryLevelDidChange:)
                                                 name:UIDeviceBatteryLevelDidChangeNotification object:nil];
    
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(batteryStateDidChange:)
                                                 name:UIDeviceBatteryStateDidChangeNotification object:nil];
    
    [self displayBatteryLevel];
    
    [self displayBatteryStatus];
    
}

#pragma mark Battery Info

- (void)displayBatteryLevel {
    float batteryLevelLocal = [UIDevice currentDevice].batteryLevel;
    if (batteryLevelLocal < 0.0)
    {
        // -1.0 means battery state is UIDeviceBatteryStateUnknown
        self.batteryLevel.text = NSLocalizedString(@"Unknown", @"");
    }
    else {
        NSNumber *levelObj = [NSNumber numberWithFloat:batteryLevelLocal];
        
        // Using the numberFormatter property lazily creates that object the
        // first time it's used. 
        self.batteryLevel.text = [self.numberFormatter stringFromNumber:levelObj];
    }    
}

- (void)displayBatteryStatus {
    // Get battery state
    switch ([UIDevice currentDevice].batteryState) {
        case UIDeviceBatteryStateUnknown:
        {
            self.chargingState.text = NSLocalizedString(@"Unknown", @"");
            break;
        }
        case UIDeviceBatteryStateUnplugged:
        {
            self.chargingState.text = NSLocalizedString(@"Unplugged", @"");
            break;
        }
        case UIDeviceBatteryStateCharging:
        {
            self.chargingState.text = NSLocalizedString(@"Charging", @"");
            break;
        }
        case UIDeviceBatteryStateFull:
        {
            self.chargingState.text = NSLocalizedString(@"Full", @"");
            break;
        }
    }    
}

#pragma mark Battery Notifications

// Called when the battery level has changed
- (void)batteryLevelDidChange:(NSNotification *)notification
{
    [self displayBatteryLevel];
}

// Clalled when the battery status has changed
- (void)batteryStateDidChange:(NSNotification *)notification
{
    [self displayBatteryStatus];
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];
    
    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    self.batteryLevel = nil;
    self.chargingState = nil;
}

- (void)viewDidDisappear:(BOOL)animated {
    [[NSUserDefaults standardUserDefaults] setInteger:2 forKey:@"WhichView"];
}


- (void)dealloc {
    [batteryLevel release];
    [chargingState release];
    [numberFormatter release];
    [super dealloc];
}


@end

The above code is commented, so it should be pretty obvious what it does. I first register for change notifications for battery level and battery status change, and display the initial values for those properties.

There is a really good example from Apple called BatteryStatus. It should give you anything you need regarding battery information.

I hope you find it useful!

Android XML Parsing

2010-02-08T10:37:00.001-05:00

If you ever considered which parser to use in Android, on developer.com you can find an article that does a comparison of DOM, SAX, and XMLPullParser. Since I started working with Java ME in 2003, SAX was the XML parser of choice, since DOM consumed to much memory and was slower. Nothing changed in Android, although the pull parser is much closer in performance to SAX.

Getting the Battery Level in Android using the SDK

2010-02-07T21:33:00.002-05:00

~~Finding out the battery level using the Android SDK is not quite an easy task because this functionality is not documented, which means it can change at any point in time~~. Well, after reading a little more about the ACTION_BATTERY_CHANGED Intent and about the BatteryManager class, starting with API Level 5, you have all the information needed to get the status on your phone's battery. The BatteryManager class contains some String values that will give you information about the current battery level and the scale, constants such as EXTRA_LEVEL and EXTRA_SCALE. If you were to work with an API version older than 2.0 (< 5), then it becomes a little more difficult to find the right information as it is not documented in the APIs as far as I could tell.

For now, here is how you can find out:

Create an IntentFilter that matches the Intent.ACTION_BATTERY_CHANGED action.
Create a BroadcastReceiver that will be called with a broadcast intent.
Inside onReceive, retrieve data based on the "level" item (battery level) for version < 5, or use BatteryManager.EXTRA_LEVEL for versions >= 5.
Register the receiver that will be called with the broadcast intent that signals a battery change

Here is the BatteryLevelActivity:

package edu.fau.csi.battery;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.widget.TextView;

/**
 * Used for finding the battery level of an Android-based phone.
 * 
 * @author Mihai Fonoage
 *
 */
public class BatteryLevelActivity extends Activity {
    /** Called when the activity is first created. */
    private TextView batterLevel;

    @Override
    /**
     * Called when the current activity is first created.
     */
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        setContentView(R.layout.main);
        batterLevel = (TextView) this.findViewById(R.id.batteryLevel);
        batteryLevel();
    }

    /**
     * Computes the battery level by registering a receiver to the intent triggered 
     * by a battery status/level change.
     */
    private void batteryLevel() {
        BroadcastReceiver batteryLevelReceiver = new BroadcastReceiver() {
            public void onReceive(Context context, Intent intent) {
                context.unregisterReceiver(this);
                int rawlevel = intent.getIntExtra("level", -1);
                int scale = intent.getIntExtra("scale", -1);
                int level = -1;
                if (rawlevel >= 0 && scale > 0) {
                    level = (rawlevel * 100) / scale;
                }
                batterLevel.setText("Battery Level Remaining: " + level + "%");
            }
        };
        IntentFilter batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
        registerReceiver(batteryLevelReceiver, batteryLevelFilter);
    }
    
}

The battery.xml layout file is next:

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout 
  xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" 
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent"> 
  
    <TextView         
        android:id="@+id/batteryLevel"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent" 
        android:gravity="center_vertical|center_horizontal"
        android:textSize="50dip"> 
    </TextView>
    
</LinearLayout>

As I mentioned in the beginning, if you are using Android 2.0 or higher, you can make the following changes to the batteryLevel method of the BatterLevelActivity class:

    /**
     * Computes the battery level by registering a receiver to the intent triggered 
     * by a battery status/level change.
     */
    private void batteryLevel() {
        BroadcastReceiver batteryLevelReceiver = new BroadcastReceiver() {
            public void onReceive(Context context, Intent intent) {
                context.unregisterReceiver(this);
                int rawlevel = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
                int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
                int level = -1;
                if (rawlevel >= 0 && scale > 0) {
                    level = (rawlevel * 100) / scale;
                }
                batterLevel.setText("Battery Level Remaining: " + level + "%");
            }
        };
        IntentFilter batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
        registerReceiver(batteryLevelReceiver, batteryLevelFilter);
    }

The code for getting the battery level was inspired from the Twisty project.

Enjoy!

Unit and Functional Testing in Android

2010-01-31T17:30:00.004-05:00

I don't have to tell you that testing is a fundamental part of the product development cycle, although I just did. No matter if you are developing for the desktop, web, or mobile space, you should make sure that the end software system works as required. This blog will go through two flavors of testing on the Android platform: unit and functional.

Unit tests tell the developer that the code runs correctly, while functional tests tell the developer that the code is doing what is supposed to do. To more clearly understand the difference, I will use the analogy mentioned in http://www.ibm.com/developerworks/library/j-test.html. If you think of building a system as being similar to building a house, then think of unit tests as having the building inspector at the construction's site, focusing on making sure that the internal system of the house (foundation, plumbing, etc) works correctly, while functional testing as having the homeowner visiting the house and being interested in how the house looks, if the rooms have the desired size, etc. He assumes that the internal functions of the house work properly.

In unit testing, think of a unit as being the smallest testable part of an application, such as a function/method. The goal is to isolate such parts and make sure they run correctly by being able to test them repeatably. Unit tests are written from the developer's perspective, and as a developer, we have to make sure that we understand the specification and requirements of our software system before writing unit tests. This can be achieved through use cases.

The flow of unit testing is shown below:

Android uses JUnit, and open source framework for writing and running unit tests. Some of the framework's features are:

Assertions for testing expected results
Test fixtures for sharing common data
Test runners for running tests

How does JUnit work? You use assert statements to assert that something is true (assertTrue(expected, actual), assertTrue(condition), etc), that something is false (assertFalse(condition), etc), that something is equal (assertEqual(expected, actual), etc). When an assert fails, the test failed for that particular case, hence your code needs to be fixed (assuming the unit test was written correctly).

Starting with version 4.x, JUnit takes advantage of Java 5 Annotations:

@Test

Mark your test cases with the @Test annotation

@Before and @After

Used for "setup" and "tearDown" methods
They run before and after every test case

@BeforeClass and @AfterClass

Used for class wide "setup" and "tearDown"
They run one time, before and after all test cases
You write you initialization code (i.e. open database connection) and cleanup code (i.e. close database connection) in here

@Ignore

Used for test cases you want to ignore (i.e. on methods that are not fully implemented yet, hence are not ready to be ran)

Exception Handling

Use the "expected" parameter with the @Test annotation for test cases that expect exceptions (i.e. @Test(expected = ArithmeticException.class) ... )

Let us look at a Java Example, namely a Calculator application. The class that incorporates the basic functionality of a calculator is shown below:

/**

package edu.fau.csi.junit;

/**
 * Simple class that incorporates the basic functionality of a calculator, providing methods to 
 * add, subtract, multiply, and divide to double numbers.  
 * 
 * @author Mihai Fonoage
 *
 */
public class Calculator {
    /**
     * Left operand of the operation to be performed.
     */
    private double leftOperand;
    /**
     * Right operand of the operation to be performed.
     */
    private double rightOperand;
    
    /**
     * Constructs a Calculator object by initializing the leftOperand and rightOperand 
     * with the given values.
     * 
     * @param leftOperand Left operand.
     * @param rightOperand Right operand.
     */
    public Calculator(double leftOperand, double rightOperand) {
        this.leftOperand = leftOperand;
        this.rightOperand = rightOperand;
    }
    
    /**
     * Adds the leftOperand to the rightOperand.
     * 
     * @return The sum of the two operands. 
     */
    public double add() {
        return leftOperand + rightOperand;
    }
    /**
     * Subtracts the rightOperand from the leftOperand.
     * 
     * @return The subtraction of the two operands. 
     */
    public double subtract() {
        return leftOperand - rightOperand;
    }
    /**
     * Multiply the leftOperand to the rightOperand.
     * 
     * @return The multiplication of the two operands. 
     */
    public double multiply() {
        return leftOperand * rightOperand;
    }
    /**
     * Divides the leftOperand to the rightOperand.
     * 
     * @return The division of the two operands. 
     */
    public double divide() {
        if (rightOperand == 0) {
            throw new ArithmeticException("right operand should not be zero!");
        }
        return leftOperand / rightOperand;
    }
}

I created a new source folder named test and included the following test class (by right-clicking on the project name -> New -> JUnit Test Case, choose "New JUnit 4 test", and as the class under test, search for the above Calculator class):

package edu.fau.csi.junit;

import static org.junit.Assert.assertTrue;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

/**
 * JUnit Test case for the Calculator class.
 * 
 * @author Mihai Fonoage
 *
 */
public class CalculatorTest {
    
    private Calculator calculator;
    
    /**
     * Sets up the test fixture. 
     * (Called before every test case method.)
     */
    @Before
    public void setUp() {
        calculator = new Calculator(6, 4);
    }

    /**
     * Tears down the test fixture. 
     * (Called after every test case method.)
     */
    @After
    public void tearDown() {
        calculator = null;
    }

    /**
     * Test method for {@link edu.fau.csi.junit.Calculator#add()}.
     */
    @Test
    public void testAdd() {
        assertTrue(calculator.add() == 10);
    }

    /**
     * Test method for {@link edu.fau.csi.junit.Calculator#subtract()}.
     */
    @Test
    public void testSubtract() {
        assertTrue(calculator.subtract() == 2);
    }

    /**
     * Test method for {@link edu.fau.csi.junit.Calculator#multiply()}.
     */
    @Test
    public void testMultiply() {        
        assertTrue(calculator.multiply() == 24);
    }
    
    /**
     * Test method for {@link edu.fau.csi.junit.Calculator#divide()}.
     */
    @Test
    public void testDivide() {
        assertTrue(calculator.divide() == 1.5);
    }

    /**
     * Test method for {@link edu.fau.csi.junit.Calculator#divide()}.
     */
    @Test(expected = ArithmeticException.class)
    public void testDivideByZero() {
        Calculator calculator = new Calculator(6, 0);
        calculator.divide();
    }

}

To run everything, right-click on the CalculatorTest class -> Run As -> JUnit Test. All five tests should pass.

Functional tests are written from the user's perspective. They confirm that the system does what the user expected it to do, based on the functional requirements of the system, hence it focuses on the behavior that users are interested in. The tester interacts with the system to determine if the behavior is correct.

In Android, functional testing is possible through the android.test.* package(s). We are going to use the same Calculator example, adapted for Android. When you create the Calculator Android project in Eclipse, choose also co create a Test Project for it. You will end up with two project, the Calculator project and the CalculatorTest project. The layout of the Calculator project is described below:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="@+id/linear" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical">
    
    <TableLayout android:id="@+id/table" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical" 
        android:stretchColumns="1">
        <TableRow>
            <TextView android:id="@+id/leftOperand_label" 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" 
                android:padding="3dip"
                android:textStyle="bold" 
                android:text="Left Operand">
            </TextView>
            <EditText android:id="@+id/leftOperand" 
                android:padding="3dip"
                android:numeric="decimal"
                android:singleLine="true"
                android:scrollHorizontally="true" 
                android:nextFocusDown="@+id/rightOperand">
            </EditText>
        </TableRow>
        <TableRow>
            <TextView android:id="@+id/rightOperand_label" 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" 
                android:padding="3dip"
                android:textStyle="bold" 
                android:text="Right Operand">
            </TextView>
            <EditText android:id="@+id/rightOperand" 
                android:padding="3dip"
                android:singleLine="true"
                android:scrollHorizontally="true"
                android:nextFocusDown="@+id/plus">
            </EditText>
        </TableRow>
    </TableLayout>
    
    <LinearLayout android:id="@+id/buttons_linear" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        
        <Button android:id="@+id/plus" 
            android:layout_width="0px"
            android:layout_height="wrap_content" 
            android:layout_weight="1"
            android:padding="6dip"
            android:text="+" 
            android:layout_gravity="center_horizontal" 
            android:nextFocusRight="@+id/minus">
        </Button>
        
        <Button android:id="@+id/minus" 
            android:layout_width="0px"
            android:layout_height="wrap_content" 
            android:layout_weight="1"
            android:padding="6dip"
            android:text="-" 
            android:layout_gravity="center_horizontal" 
            android:nextFocusRight="@+id/multiply">
        </Button>
        
        <Button android:id="@+id/multiply" 
            android:layout_width="0px"
            android:layout_height="wrap_content" 
            android:layout_weight="1"
            android:padding="6dip"
            android:text="*" 
            android:layout_gravity="center_horizontal" 
            android:nextFocusRight="@+id/divide">
        </Button>
        
        <Button android:id="@+id/divide" 
            android:layout_width="0px"
            android:layout_height="wrap_content" 
            android:layout_weight="1"
            android:padding="6dip"
            android:text="/" 
            android:layout_gravity="center_horizontal" 
            android:nextFocusRight="@+id/divide">
        </Button>
        
        <Button android:id="@+id/clear" 
            android:layout_width="0px"
            android:layout_height="wrap_content" 
            android:layout_weight="1"
            android:padding="6dip"
            android:text="C" 
            android:layout_gravity="center_horizontal" 
            android:nextFocusRight="@+id/divide">
        </Button>
        
    </LinearLayout>
    
    <TextView android:id="@+id/result" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" 
        android:padding="20dip"
        android:textStyle="bold" 
        android:gravity="right"
        android:text="Result">
    </TextView>
    
</LinearLayout>

It is a simple layout, with two initial text fields for the left and right operand, five buttons, each for one operation, plus a clear button, and one text field that will hold the result of the calculation. As a side note, I have put the text for each of these elements inside the layout xml file to save some time; you should put them inside the strings.xml file instead.

The CalculatorActivity class is described next:

package edu.fau.csi.calculator;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class CalculatorActivity extends Activity implements OnClickListener {

    private EditText leftOperand;

    private EditText rightOperand;

    private TextView result;
    
    private Calculator calculator;
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.calculator);
                        
        leftOperand = (EditText)findViewById(R.id.leftOperand);
        rightOperand = (EditText)findViewById(R.id.rightOperand);
        result = (TextView)findViewById(R.id.result);

        Button plus = (Button)findViewById(R.id.plus);
        plus.setOnClickListener(this);
        Button minus = (Button)findViewById(R.id.minus);
        minus.setOnClickListener(this);
        Button multiply = (Button)findViewById(R.id.multiply);
        multiply.setOnClickListener(this);
        Button divide = (Button)findViewById(R.id.divide);
        divide.setOnClickListener(this);
        Button clear = (Button)findViewById(R.id.clear);
        clear.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        double leftOp = Double.parseDouble(leftOperand.getText().toString());
        double rightOp = Double.parseDouble(rightOperand.getText().toString());
        calculator = new Calculator(leftOp, rightOp);
        
        if (view.getId() == R.id.plus) {
            result.setText("" + calculator.add());
        }
        else if (view.getId() == R.id.minus) {
            result.setText("" + calculator.add());
        }
        else if (view.getId() == R.id.multiply) {
            result.setText("" + calculator.multiply());
        }
        else if (view.getId() == R.id.divide) {
            result.setText("" + calculator.divide());
        }
        else if (view.getId() == R.id.clear) {
            leftOperand.setText("");
            rightOperand.setText("");
            result.setText("");
            leftOperand.requestFocus();
        }
    }
}

The Calculator class that actually does the calculations is exactly the same as the one from the Java example.

When you run this example, you will get the following screen:

The unit testing part is the same as the one mentioned in the unit testing section of this blog. You can still test your business logic without needing to interact with the application through its user interface. Actually, Calculator.java and CalculatorTest.java were just copied from the Java example to the Android without making any modifications.

Functional testing for this example involves the process of entering numbers in the two text fields, pressing one of the operations button, and checking the result to make sure it is the expected one. Instead of having the developer/user/tester do this manually, we can automate the task by sending key events through instrumentation, all from the CalculatorActivityTest class from the CalculatorTest application:

package edu.fau.csi.calculator.test;

import android.test.ActivityInstrumentationTestCase2;
import android.view.KeyEvent;
import android.widget.TextView;
import edu.fau.csi.calculator.CalculatorActivity;


public class CalculatorActivityTest extends ActivityInstrumentationTestCase2<CalculatorActivity>{

    private TextView result;

    private CalculatorActivity calculatorInstance;

    public CalculatorActivityTest() {
        super("edu.fau.csi.calculator", CalculatorActivity.class);
    }

    /* (non-Javadoc)
     * @see android.test.ActivityInstrumentationTestCase2#setUp()
     */
    @Override
    protected void setUp() throws Exception {
        // TODO Auto-generated method stub
        super.setUp();
        calculatorInstance = (CalculatorActivity) getActivity();
        result = (TextView)calculatorInstance.findViewById(R.id.result);
    
    }

    /**
     * Test the addition operation of the CalculatorActivity
     * 
     * @throws Throwable
     */
    public void testAdd() throws Throwable {
        
        //First field value
        sendKeys( KeyEvent.KEYCODE_3 );
        sendKeys( KeyEvent.KEYCODE_PERIOD );
        sendKeys( KeyEvent.KEYCODE_5 );
        
        //Move to the second field
        sendKeys( KeyEvent.KEYCODE_DPAD_DOWN );
        sendKeys( KeyEvent.KEYCODE_2 );
        sendKeys( KeyEvent.KEYCODE_PERIOD );
        sendKeys( KeyEvent.KEYCODE_1 );

        //Move to the '+' button
        sendKeys( KeyEvent.KEYCODE_DPAD_DOWN );
        sendKeys( KeyEvent.KEYCODE_DPAD_CENTER );

        //Wait for the activity to finish all of its processing.
        getInstrumentation().waitForIdleSync();
        
        //Use assertion to make sure the value is correct
        assertTrue(result.getText().toString().equals("5.6"));
        
    } 
}

The above activity test class inherits from the ActivityInstrumentationTestCase2 that provides functional testing of a single activity, namely our CalculatorActivity. The above code only tests the add method, but similar implementations can be done for all other three calculations.

The Android manifest file for the CalculatorTest project is described next:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="edu.fau.csi.calculator.test"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">

    <uses-library android:name="android.test.runner" />
    </application>
    <uses-sdk android:minSdkVersion="4" />
    <instrumentation android:targetPackage="edu.fau.csi.calculator" 
        android:name="android.test.InstrumentationTestRunner" />
</manifest>

When the activity is ran for the first time, you have to create a new Android JUnit Test configuration. There are two possibilities, both shown below:

When you run this, the Calculator application will start in the emulator, you will see the two text fields being populated with the values 3.5 and 2.1, the "+" button being pressed, and the result field populated with the result of the operation, namely 5.6.

I hope you find this helpful!

Are students prepared for working in the industry?

2010-01-12T15:57:00.004-05:00

This should have actually been a two-part blog, first talk about the fact that there are now course on iPhone and Android programming offered at my university, and second transition to the topic mentioned in the title of the blog, namely the existing gap between what we are thought in school, and what is actually needed outside in the industry. Just by the fact that such courses are being offered, I believe that the gap is getting a little smaller. Read on to get a feel of what I think about all this.

I had my first lecture as part of the iPhone Programming class offered at FAU (similar to the course offered at Stanford and available online for free) I am excited because mobile development has been a passion of mine for some time now. I have been working with J2ME since my fourth year of college (2004), and with Android since before its official 1.0 release. Both platforms come with their advantages and shortcomings. Now, the opportunity to take part of the iPhone class could not be left unanswered, hence I enrolled for the Spring semester as part of my last class moving toward the end of my PhD.

I wanted to look into iPhone programming for some time now, but there were some impediments like not owning a Mac, and not having time for it. Well, my first problem was solved because, graciously enough, our CEECS department at FAU has created an advanced Apple Lab that comes with 10 Macs and 5 iPod Touch. My second problem got solved due to the fact that I had to take one more class, so why not make it one that is all about mobile programming. At the end of the class, I could better compare and contrast the different mobile platforms that I am familiar with.

I had some (minor) complaints about the curricula here at FAU. I felt that the courses being thought are somewhat out of touch with the need of the industry. And because most of the students end up working in the industry, better choices for courses could be offered. I have a whole list of classes that I wish would be offered here, and I am going to share this with list with you (letting me know what other classes you think would be useful):

Web Services (SOA more generally)
Software Testing (Black/White Box, Integration/Regression/Acceptance/Unit Testing, TDD)
Java and C# (and here maybe more on the Enterprise side with Java EE and .NET)
Compilers
Project Management (Lean, Agile (XP, Scrum), RUP, V-MODEL)
Functional and Logical Programming
Distributed Systems
Math for Computer Science
Web Developemnt (in terms of Rails, PhP, Flash, Perl, Python, GWT)
Software Security (Encryption, SSL/TSL, HTTPS, Cyphers, Hashes, etc)

Mobile Development class that would include Java ME, Android, and iPhone Programming, was also on the list but fortunately enough, Android and iPhone Programming are currently being taught here at FAU (I am much involved in the Android class, not as a student, but as a teaching assistant). Refactoring was also on the list, but having a whole class on this topic seems a little too much (instead it could be incorporated in any programming class available).

I recently read an article written by Bjarne Stroustrup entitled "What Should We Teach New Software Developers? Why", that expressed some of the feelings I have on this topic. Although there is still room for improvement, I do believe that we (FAU, but I am sure some universities were already on this path for some time) are going in the right direction offering courses that are useful when graduating from school.

Must-Read Software Development Resources for 2009

2010-01-05T04:51:00.002-05:00

At the end of last year, Dustin Marx wrote a blog about the Must-Read Software Development Resources for 2009, where he mentions useful blogs and articles for software developers. You'll find information ranging from discussion on simplicity to the existing gap between academia and industry (article written by Stroustrup, and the one I found most interesting of all).

If you find yourself wanting more, the last two links are to other ten papers that "every programmer should read", and you should read them as they are really insightful.

A couple of short links - December 24, 2009

2009-12-24T08:12:00.001-05:00

1. 16 Cool Cellphone Concepts Which Won't Be Implemented - cellphone concepts that look amazing, ranging from customizable back sides like the Nokia Unik, to cellphones that act as a bangle like the LG Helix.

2. The (Last and Next) Decade in Gadgets - breakthroughs in technology of the past decade and prediction of future trends. The areas covered are Computers/OS, Cellphones, Web, cameras, Home Entertainment, Music, Movies, Video Games (here it mentions Microsoft's Natal project), and Print.

3. Top Ten Stories on Digg in 2009 - the title says it all.

4. Java Design Patterns book - written by IBM's James Cooper, an excellent free resource on Design Patterns implemented in Java. Bruce Eckel has a similar book, entitled Thinking in Patterns.

Cross-Platform Mobile Development

2009-12-22T07:48:00.008-05:00

I don't have to tell you that there are multiple mobile platforms out there, such as Symbian, Blackberry, iPhone, Android, Windows Mobile, BREW, webOS, Limo, Bada, and others. As a mobile applications developer, one should try to cover as many platforms as possible. Developing on these platforms requires knowledge of Java, C++, .NET, Objective-C, clearly too many languages. As if this would not be enough, there is the fragmentation issue within each platform. So, what can one do to alleviate these problems? Fortunately, there are some tools that mitigate this issue by allowing to design/code once, and port to different platforms afterwards. I am just going to mention some of them, leaving up to you to go and further investigate if you deem necessary. A quick note: when HTML is mentioned, JavaScript and CSS are included by default.

Airplay allows you to code in Visual C++ and build for x86 and ARM compilers, thus building your application as an "OS-agnostic binary file that contains native CPU instructions". The platforms supported are iPhone, Android, Symbian, Windows Mobile, and BREW.

Alchemo is useful if you have a Java ME application that has to be ported to other platforms such as Android, BREW, iPhone, and Windows Mobile.

PhoneGap is an open source tool for web developers that want to take advantage of features such as location, accelerometer, etc, and still write applications using HTML. The platforms supported are iPhone, Android, Blackberry, Palm, and Windows Mobile.

With Pyxis Mobile, you can take advantage of their Application Studio and configure your application to run on Blackberry, Windows Mobile, and iPhone platforms. The platform offers support for connectivity to enterprise data sources.

Rhodes is an open source framework where you can build native applications (despite the use of HTML or Ruby for development) that run on the iPhone, Windows Mobile, Blackberry, Symbian, and Android.

Smartface Designer allows you to design you application using the tool and deploy it to Blackberry, Symbian, and J2ME. You can drag-and-drop existing components when using the designer tool, thus avoiding writing code.

Sybase Unwired Platform follows the same line of designing your applications once, and deploy it on several mobile platforms such as Windows Mobile, Windows 32 (Laptops/Tablets), iPhone, and Blackberry. The platforms is geared towards enterprise, offering integration with Sybase, Oracle, IBM, and Microsoft based databases, SAP, Remedy, etc enterprise applications, and Web Services.

Titanium Mobile uses Web Technologies (such as HTML, JavaScript, etc) to build native applications for the iPhone and Android platforms.

Voyager allows you to code in your favorite development language (Java, .NET languages, C++), and deploy it on various platforms such as Android, JavaFX, Windows Mobile, Java ME, Linux, Blackberry, Symbian, BREW, iPhone, with future support for Real-Time OSs. This is the platform that covers most of the existing mobile platforms, and allows for enterprise integration.

Other platforms that may be worth looking into are Dexterra Concert, Spring Wireless, and QuickConnect.

Below is a table summarizing the info supplied above (last updated on: July 17, 2010):

	Airplay	Alchemo	PhoneGap	Pyxis Mobile App Studio	Rhodes	Smartface Designer	Sybase Unwired Platform	Titanium Mobile	Voyager
Platforms Supported
Android	X	X	X		X			X	X
Java FX									X
Windows Mobile	X	X	X	X	X		X		X
Linux									X
Blackberry			X	X	X	X	X		X
Symbian	X		X		X	X			X
BREW	X	X							X
iPhone	X	X	X	X	X		X	X	X
Java ME						X			X
Development Languages
C++	X								X
Java ME		X
Java									X
.NET									X
HTML			X		X			X
Own Visual Language				X		X	X
Other Properties
Open Source			X		X
Enterprise Integration				X			X		X
Free	X (only for iPhone)		X		X (if using GPL)

There will be a book that will come out on ~~April of 2010~~ August 31, 2010 entitled "Pro Smartphone Cross-Platform Development: iPhone, Blackberry, Windows Mobile and Android Development and Distribution", by Sarah Allen and Vidal Graupera, and which should offer valuable resource for anyone involved with cross-platform development.

Please drop me a message if you know of any other cross-platform tool(s) worth mentioning.

Sliding Puzzle Full - First Review

2009-12-15T10:35:00.003-05:00

I found the first review of my Android game, Sliding Puzzle Full, review made for an older version (1.0.0). I am glad James enjoyed the game. From the review:

"Sliding Puzzle Full v1.1.0 is a fun application that makes your photos take on a whole new life of their own. I liked the grid size option and the ability to choose a picture or create a new puzzle using my phones camera.

The controls are overall simple to use, the touchscreen sliding mechanism is very functional and the program offers simple fun. If you're a puzzler fan you'll love this game."

Some notes:

- the game is available on Android Market, but it was built with version 1.6, hence some phones might not *see* it yet.

- I will not update the slideme version of the game (which is 1.0.0). The newest version is 1.1.1 and can be found in the Android Market.

Displaying Images from SD Card In Android - Part 2

2009-11-22T18:04:00.005-05:00

In one of my previous posts, I wrote about how to fetch and display images from the SD card. The problem with the previous post is that one would have to wait until the first couple of images are available and shown on the screen. This implies that when the user wants to see the images, he will wait a couple of seconds until the first screen of images is available. The code that I'm going to post here works more like the Gallery application, meaning that one image at a time will be displayed on the screen. To achieve this effect, I used an AsyncTask, which fetches one image at a time in the background, and adds that image to the grid view during the progress update.

package blog.android.sdcard2;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Display;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemClickListener;

/**
 * Loads images from SD card. 
 * 
 * @author Mihai Fonoage
 *
 */
public class LoadImagesFromSDCardActivity extends Activity implements
OnItemClickListener {
    
    /**
     * Grid view holding the images.
     */
    private GridView sdcardImages;
    /**
     * Image adapter for the grid view.
     */
    private ImageAdapter imageAdapter;
    /**
     * Display used for getting the width of the screen. 
     */
    private Display display;

    /**
     * Creates the content view, sets up the grid, the adapter, and the click listener.
     * 
     * @see android.app.Activity#onCreate(android.os.Bundle)
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        
        // Request progress bar
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.sdcard);

        display = ((WindowManager) getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();

        setupViews();
        setProgressBarIndeterminateVisibility(true); 
        loadImages();
    }

    /**
     * Free up bitmap related resources.
     */
    protected void onDestroy() {
        super.onDestroy();
        final GridView grid = sdcardImages;
        final int count = grid.getChildCount();
        ImageView v = null;
        for (int i = 0; i < count; i++) {
            v = (ImageView) grid.getChildAt(i);
            ((BitmapDrawable) v.getDrawable()).setCallback(null);
        }
    }
    /**
     * Setup the grid view.
     */
    private void setupViews() {
        sdcardImages = (GridView) findViewById(R.id.sdcard);
        sdcardImages.setNumColumns(display.getWidth()/95);
        sdcardImages.setClipToPadding(false);
        sdcardImages.setOnItemClickListener(LoadImagesFromSDCardActivity.this);
        imageAdapter = new ImageAdapter(getApplicationContext()); 
        sdcardImages.setAdapter(imageAdapter);
    }
    /**
     * Load images.
     */
    private void loadImages() {
        final Object data = getLastNonConfigurationInstance();
        if (data == null) {
            new LoadImagesFromSDCard().execute();
        } else {
            final LoadedImage[] photos = (LoadedImage[]) data;
            if (photos.length == 0) {
                new LoadImagesFromSDCard().execute();
            }
            for (LoadedImage photo : photos) {
                addImage(photo);
            }
        }
    }
    /**
     * Add image(s) to the grid view adapter.
     * 
     * @param value Array of LoadedImages references
     */
    private void addImage(LoadedImage... value) {
        for (LoadedImage image : value) {
            imageAdapter.addPhoto(image);
            imageAdapter.notifyDataSetChanged();
        }
    }
    
    /**
     * Save bitmap images into a list and return that list. 
     * 
     * @see android.app.Activity#onRetainNonConfigurationInstance()
     */
    @Override
    public Object onRetainNonConfigurationInstance() {
        final GridView grid = sdcardImages;
        final int count = grid.getChildCount();
        final LoadedImage[] list = new LoadedImage[count];

        for (int i = 0; i < count; i++) {
            final ImageView v = (ImageView) grid.getChildAt(i);
            list[i] = new LoadedImage(((BitmapDrawable) v.getDrawable()).getBitmap());
        }

        return list;
    }
    /**
     * Async task for loading the images from the SD card. 
     * 
     * @author Mihai Fonoage
     *
     */
    class LoadImagesFromSDCard extends AsyncTask<Object, LoadedImage, Object> {
        
        /**
         * Load images from SD Card in the background, and display each image on the screen. 
         *  
         * @see android.os.AsyncTask#doInBackground(Params[])
         */
        @Override
        protected Object doInBackground(Object... params) {
            //setProgressBarIndeterminateVisibility(true); 
            Bitmap bitmap = null;
            Bitmap newBitmap = null;
            Uri uri = null;            

            // Set up an array of the Thumbnail Image ID column we want
            String[] projection = {MediaStore.Images.Thumbnails._ID};
            // Create the cursor pointing to the SDCard
            Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
                    projection, // Which columns to return
                    null,       // Return all rows
                    null,       
                    null); 
            int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
            int size = cursor.getCount();
            // If size is 0, there are no images on the SD Card.
            if (size == 0) {
                //No Images available, post some message to the user
            }
            int imageID = 0;
            for (int i = 0; i < size; i++) {
                cursor.moveToPosition(i);
                imageID = cursor.getInt(columnIndex);
                uri = Uri.withAppendedPath(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID);
                try {
                    bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri));
                    if (bitmap != null) {
                        newBitmap = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
                        bitmap.recycle();
                        if (newBitmap != null) {
                            publishProgress(new LoadedImage(newBitmap));
                        }
                    }
                } catch (IOException e) {
                    //Error fetching image, try to recover
                }
            }
            cursor.close();
            return null;
        }
        /**
         * Add a new LoadedImage in the images grid.
         *
         * @param value The image.
         */
        @Override
        public void onProgressUpdate(LoadedImage... value) {
            addImage(value);
        }
        /**
         * Set the visibility of the progress bar to false.
         * 
         * @see android.os.AsyncTask#onPostExecute(java.lang.Object)
         */
        @Override
        protected void onPostExecute(Object result) {
            setProgressBarIndeterminateVisibility(false);
        }
    }

    /**
     * Adapter for our image files. 
     * 
     * @author Mihai Fonoage
     *
     */
    class ImageAdapter extends BaseAdapter {

        private Context mContext; 
        private ArrayList<LoadedImage> photos = new ArrayList<LoadedImage>();

        public ImageAdapter(Context context) { 
            mContext = context; 
        } 

        public void addPhoto(LoadedImage photo) { 
            photos.add(photo); 
        } 

        public int getCount() { 
            return photos.size(); 
        } 

        public Object getItem(int position) { 
            return photos.get(position); 
        } 

        public long getItemId(int position) { 
            return position; 
        } 

        public View getView(int position, View convertView, ViewGroup parent) { 
            final ImageView imageView; 
            if (convertView == null) { 
                imageView = new ImageView(mContext); 
            } else { 
                imageView = (ImageView) convertView; 
            } 
            imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
            imageView.setPadding(8, 8, 8, 8);
            imageView.setImageBitmap(photos.get(position).getBitmap());
            return imageView; 
        } 
    }

    /**
     * A LoadedImage contains the Bitmap loaded for the image.
     */
    private static class LoadedImage {
        Bitmap mBitmap;

        LoadedImage(Bitmap bitmap) {
            mBitmap = bitmap;
        }

        public Bitmap getBitmap() {
            return mBitmap;
        }
    }
    /**
     * When an image is clicked, load that image as a puzzle. 
     */
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {        
        int columnIndex = 0;
        String[] projection = {MediaStore.Images.Media.DATA};
        Cursor cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
                projection,
                null, 
                null, 
                null);
        if (cursor != null) {
            columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            cursor.moveToPosition(position);
            String imagePath = cursor.getString(columnIndex); 

            FileInputStream is = null;
            BufferedInputStream bis = null;
            try {
                is = new FileInputStream(new File(imagePath));
                bis = new BufferedInputStream(is);
                Bitmap bitmap = BitmapFactory.decodeStream(bis);
                Bitmap useThisBitmap = Bitmap.createScaledBitmap(bitmap, parent.getWidth(), parent.getHeight(), true);
                bitmap.recycle();
                //Display bitmap (useThisBitmap)
            } 
            catch (Exception e) {
                //Try to recover
            }
            finally {
                try {
                    if (bis != null) {
                        bis.close();
                    }
                    if (is != null) {
                        is.close();
                    }
                    cursor.close();
                    projection = null;
                } catch (Exception e) {
                }
            }
        }
    }

}

The sdcard.xml file:

<?xml version="1.0" encoding="utf-8"?>

<FrameLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    
    <GridView  
        android:id="@+id/sdcard"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:verticalSpacing="10dp"
        android:horizontalSpacing="10dp" 
        android:stretchMode="columnWidth"
        android:gravity="center" />
        
</FrameLayout>

That's it. Let me know if you have any questions.

Enjoy!

Gartner's Top 10 Mobile Apps for 2012

2009-11-18T22:09:00.001-05:00

Gartner has released its top 10 applications for 2012.

"Consumer mobile applications and services are no longer the prerogative of mobile carriers,” said Sandy Shen, research director at Gartner. “The increasing consumer interest in smartphones, the participation of Internet players in the mobile space, and the emergence of application stores and cross-industry services are reducing the dominance of mobile carriers. Each player will influence how the application is delivered and experienced by consumers, who ultimately vote with their attention and spending power".

LBS applications are at number 2. The LBS user base is predicted to grow to 526 million by 2012 (from 96 million in 2009). NFC is at number 7. I read here that some new version of iPhone is supposed to include NFC support (actually support for proximity), and I do believe it's about time for the mobile industry to get behind this technology.

You can read the entire report at Gartner.

Engineering Achievements and Challenges

2009-11-13T11:08:00.000-05:00

The National Academy of Engineering (NAE) put together two lists: one that ranks the 20 greatest engineering achievements of the 20th century, and one with engineering's challenges to be accomplished:

SOURCE: IEEE Spectrum

Android Sliding Puzzle

2009-11-12T07:46:00.003-05:00

Yesterday I released my first Android application into the Android Market. The application is a sliding puzzle game, and comes into two flavors, a free (lite) version (called "Sliding Puzzle Lite"), and a full version ("Sliding Puzzle Full") at $0.99. The lite version has only the basic features, such as 9 pre-loaded images and the ability to view the full (final) image during game play. The full version has the following features:

pre-loaded with 9 images
4 difficulty levels (3x3, 4x4, 5x5, 6x6)
shuffle puzzle image
view final image
load image from SD Card
take a picture using the Camera and load it as a puzzle
displays a timer during game play
displays how much percentage of the puzzle is done
displays the number of moves made

Below are some screen shots of the application:

I want to make some observations about the entire process.

First, the design was far from optimum in the first iteration; it was too complex for a one-screen game (one main screen, namely the puzzle screen). I started refactoring when I had to add some features and I noticed how hard it was to do just that. I ended up getting rid of some classes, methods, and instance variables all together, simplifying the design. Efficiency is crucial when developing for mobile devices. My background is in Java ME, where the restrictions are even bigger than on Android-based smartphones. For example, because I had to work with key-value pairs, instinctively I first went with a HashMap. I notice that the key-value pairs where actually pairs of integers, so I switched to using a SparseIntArray, which is more efficient that a HashMap. An even better approach would have been to use to parallel arrays of ints, but that's exactly how the SparseIntArray class is implemented, thank you for that! Overall, I tried to follow the guidelines form Designing for Performance document. Hence, the entire process was an iterative/incremental one, based on add feature <=> test feature <=> fix bugs <=> refactor (I hope the model does not look like a waterfall one because it wasn't :)). I noticed that testing and fixing bugs took the most time (and I am sure I still have bugs left unnoticed by me). I have been testing for the past month (and I've been doing all this in my spare time, being that I am working on my PhD also). Testing was still done manually (I hate that I do not use some kind of unit testing in Android). My biggest problem was that I was getting out of memory exceptions when loading bitmaps (especially when loading from SD card). I ended up using Bitmap.createScaledBitmap method to scale the bitmaps down. Furthermore, having the bitmaps displayed on the screen was initially done in a 'bulk' manner, where the screen would freeze until the first couple of images could be displayed. That's not user friendly at all; reading some blogs from smarter people, I ended up using a AsyncTask, where each image I would load, I would display on the screen, one at a time. With that, you would images being loaded on the display, similar to how the Gallery application (that comes pre-loaded on the phone) works.

Second, nothing beats testing on a real device. Emulators do come close, but having a device made quite a difference. For example, on some G1 phones, the camera software has a known bug, namely that the camera preview does not work in portrait mode. This issue is of course non-existent in the emulator.

I keep telling fellow students that I work with (or teach to), that nothing beats writing applications. Sure, you can read books (which of course you have to do), run examples, but if you do not start coding, you will never get to the next level as a programmer.

There are other lessons I have learned, and maybe I will post them in a later post.

Overall, I am looking forward to adding new features to the full version of the game (such as speech recognition, integration with Facebook, and many more), and also developing the next game from the list of ideas that I have.

I hope you enjoy the sliding puzzle, at least as much as I enjoyed developing it!

The Future of UI Design

2009-11-07T08:50:00.001-05:00

Microsoft's vision of how the future of user interface design will look like:

Beyond BigTable - Spanner

2009-10-31T09:14:00.002-04:00

BigTable is a distributed storage system designed to work in very large distributed systems where you have petabytes of data on thousands of servers. It is currently used in over 100 projects such as Google Earth, Google Maps, Blogger, Orkut, and many more.

However, there is some current work at Google on a new storage and computation system called Spanner. Some of its main characteristics:

Automation: moves and replicates data based on usage and constraints patterns.
Use of hierarchical directories (instead of rows as it is in BigTable).
Support of distributed transactions
Fine grained access control on the data
String consistency across tablet replicas
Scale to 10M machines and 1k petabytes of data, across 1000s of locations

There is a keynote talk by Jeff Dean of Google on "Design, Lessons and Advice from Building Large Distributed Systems" that talks about large distributed systems and includes topics on BigTable and Spanner. You can view the slides of the presentation here.

Current and upcoming Android Phones

2009-10-21T10:45:00.002-04:00

WiseAndroid has gathered a list of 50+ Android Phones that are currently on the market or will become available in the near future. TechCrunch provides images for (some of) the phones. Thank you for the effort!

Performance Comparison of Major Web Browsers

2009-10-15T13:33:00.001-04:00

Six Revisions has published a performance comparison of the major five web browsers (Firefox, Chrome, IE, Opera, and Safari) in terms of JavaScript speed, CPU usage under stress, DOM selection, CSS rendering speed, page load time, and browser cache performance. Bottom line, Google Chrome 3.0 wins in four out of the six performance indicators, coming third and second in the DOM Selection Speed (won by Opera) and Page Load Time (won by Firefox) tests.

Free Java and Java EE eBooks

2009-10-02T15:14:00.000-04:00

A list if free eBooks on Java and Java EE technologies: http://www.interviewjava.com/2009/09/ebooks-on-java-javaee-technologies.html.

Displaying images from SD card in Android

2009-09-28T12:43:00.016-04:00

Below you will find a Android example of how to access and display images that are stored on your SD card.

I wrote part 2 for this article, where images are loaded in the background using an asynchronous task. It is an improvement over this article, but I strongly suggest trying this one first to fully appreciate the differences between the two approaches.

The main idea is to make use of the MediaStore class, which is a Media provider that contains data for all available media on both internal and external storage devices (such as an SD card). An adapter is used as a bridge between the data and the view.

The activity is shown below:

package blog.android.sdcard;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemClickListener;

/**
 * Displays images from an SD card.
 */
public class SDCardImagesActivity extends Activity {

    /**
     * Cursor used to access the results from querying for images on the SD card.
     */
    private Cursor cursor;
    /*
     * Column index for the Thumbnails Image IDs.
     */
    private int columnIndex;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sdcard);

        // Set up an array of the Thumbnail Image ID column we want
        String[] projection = {MediaStore.Images.Thumbnails._ID};
        // Create the cursor pointing to the SDCard
        cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
                projection, // Which columns to return
                null,       // Return all rows
                null,
                MediaStore.Images.Thumbnails.IMAGE_ID);
        // Get the column index of the Thumbnails Image ID
        columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);

        GridView sdcardImages = (GridView) findViewById(R.id.sdcard);
        sdcardImages.setAdapter(new ImageAdapter(this));

        // Set up a click listener
        sdcardImages.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView parent, View v, int position, long id) {
                // Get the data location of the image
                String[] projection = {MediaStore.Images.Media.DATA};
                cursor = managedQuery( MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
                        projection, // Which columns to return
                        null,       // Return all rows
                        null,
                        null);
                columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                cursor.moveToPosition(position);
                // Get image filename
                String imagePath = cursor.getString(columnIndex);
                // Use this path to do further processing, i.e. full screen display
            }
        });
    }

    /**
     * Adapter for our image files.
     */
    private class ImageAdapter extends BaseAdapter {

        private Context context;

        public ImageAdapter(Context localContext) {
            context = localContext;
        }

        public int getCount() {
            return cursor.getCount();
        }
        public Object getItem(int position) {
            return position;
        }
        public long getItemId(int position) {
            return position;
        }
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView picturesView;
            if (convertView == null) {
                picturesView = new ImageView(context);
                // Move cursor to current position
                cursor.moveToPosition(position);
                // Get the current value for the requested column
                int imageID = cursor.getInt(columnIndex);
                // Set the content of the image based on the provided URI
                picturesView.setImageURI(Uri.withAppendedPath(
                        MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID));
                picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER);
                picturesView.setPadding(8, 8, 8, 8);
                picturesView.setLayoutParams(new GridView.LayoutParams(100, 100));
            }
            else {
                picturesView = (ImageView)convertView;
            }
            return picturesView;
        }
    }
}

The layout of the main activity is shown below:

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/sdcard"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:verticalSpacing="10dp"
    android:horizontalSpacing="10dp"
    android:numColumns="auto_fit"
    android:columnWidth="90dp"
    android:stretchMode="columnWidth"
    android:gravity="center"
/>

In order for this to work, you need to emulate an SD card.

Enjoy!

UPDATE (October 19, 2009): In order to be bale to view thumbnails images from the SD Card, Android needs to create them first, hence you should start the Gallery application that comes preinstalled, and open the sdcard folder which will automatically create thumbnails for the images stored on your sdcard. This is a current shortcoming of the SDK that will be fixed in future releases (http://groups.google.com/group/android-developers/browse_thread/thread/3f01b284e2537312/fa9487d19db4907e).

UPDATE (October 07, 2009): For some reason, if you use

MediaStore.Images.Thumbnails.IMAGE_ID

like in the previous version of the above code, the images are not always displayed on the screen. Changing to

MediaStore.Images.Thumbnails._ID

seems to solve the problem. I will look more into why and get back to you.

Furthermore, some images have the wrong path attached to them. I changed the creation of the cursor object from

cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null,       // Return all rows
null,
null);

cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
projection, // Which columns to return
null,       // Return all rows
null,
MediaStore.Images.Thumbnails.IMAGE_ID);

Dilbert comic strip - Sep 11, 2009

2009-09-16T12:30:00.004-04:00

You got to have a sense of humor to enjoy this, especially in this hard economic times.

Global smartphone market shares

2009-08-27T16:33:00.014-04:00

From the data findings by analyst company Canalys, while Nokia and Microsoft shares are decreasing, RIM and Apple are growing:

The above stats are based on the number of units shipped during Q2 of 2009. The iPhone 3G was not yet out when the data was gathered. Android-based smartphones where not available in the second quarter of 2008. By this time next year, Android will be much closer to Microsoft's share. Nokia just came out with its Maemo-based smartphone, the N900. Moving more towards Maemo rather than hanging on to Symbian might actually work out pretty well for Nokia in the end.

Satisfiability Problems Online Game

2009-08-27T09:40:00.009-04:00

There's an article in the IEEE Spectrum regarding Crowdsourcing the Complexities of Electronic Design Automation, which talks about a game called FunSAT that could benefit chip makers in improving their designs. Humans can help at this stage because these kind of problems are difficult for computers to solve. The game simulates satisfiability problems (SATs), and presents the user with a set of buttons and bubbles, where the buttons can have a value of true, false, or unassigned, and the bubbles, which represent clauses, can be satisfied, unsatisfied, or undetermined. The goal is to turn all bubbles green. For a bubble to turn green, at least one of the literals in the corresponding clause must be true. If all of the literals are false, the bubble will turn red; otherwise, it will be gray.

Why are satisfiability problems important? Because they aid in the design verification stage of chip design. "For example, they are used to find out what input combinations result in exposing a potential bug in the design. If no such combination exists, then the designers don’t have to worry about that particular bug."

"Modern satisfiability solvers tend to prioritize and limit their searches to a few paths that look promising. By using this method, however, they don’t always find the best configuration. What humans lack in brute-force speed, they tend to make up for with pattern recognition and intuition—the ability to know a good move without being able to explain why it’s good. And, most important, they like to play games."

Invoke a Web Service from JSP

2009-08-21T09:35:00.073-04:00

This tutorial is a small example on how to call a SOAP-based Web Service from a browser-based client (using HTML and JSP). As an application server, we will use GlassFish. When you download GlassFish, make sure you use the preview version for this tutorial.

The example takes a number as its input and computes the corresponding Fibonacci number. We will start with the Web Service:

package blog.webservice;

import javax.jws.WebMethod;
import javax.jws.WebService;

@WebService
public class FibonacciNumber {

@WebMethod
public int fibNum(int n) {
int first = 1, fib = 1;
for (int i = 3; i <= n; i++) {
int temp = first + fib;         
first = fib;         
fib = temp;         
}     
return fib;     
}
}

After compilation of the above code, you take the resulting class file and copy it to the blog/WEB-INF/classes/blog/webservice directory. Next step is to package the WEB-INF directory into a WAR file for deployment by executing the following command:

% jar cvf fib.war WEB-INF

The WAR is then copied to GLASSFISH_HOME/domains/domain1/autodeploy, where GLASSFISH_HOME points to the GlassFish install directory. If the deployment succeeds, a second file named fib.war_deployed appears in a few seconds in the autodeploy directory.

The good part about GlassFish is that you do not need to manually (using wsgen) generate the JAX-B artifacts that the service requires, because the current Metro web services stack release ships with GlassFish, automatically generating these artifacts. The WSDL file is also automatically generated and will be used on the client side as described in one of the sections below.

To generate the client-side artifacts (client.FibonacciNumber, client.FibonacciNumberService, etc), we will use wsimport on the wsdl file generated aytomatically by GlassFish:

wsimport -keep -p client http://localhost:8080/fib/FibonacciNumberService?wsdl

Next step is writing the client-side code, namely the HTML page, two JSP pages, and one xml configuration file.

The HTML page is simple and straightforward:

<html>
<body>
<form method = 'POST' action = 'fib.jsp'>
Input number for Fibonacci: <input type = 'text' name = 'inputNumber'><br/><hr/>
<input type = 'submit' value = ' Get Fibonacci '/>
</form>
</body>
</html>

The actual JSP that will invoke the FibonacciNumber web service is below:

<%@ page errorPage = 'errors.jsp' %>
<%@ page import = "client.FibonacciNumber" %>
<%@ page import = "client.FibonacciNumberService" %>
<html>
<body>
<%! private int fibNo, temp; %>
<%
String inputString = request.getParameter("inputNumber");
if (inputString != null) {
temp = Integer.parseInt(inputString.trim());
}

FibonacciNumberService service =  new FibonacciNumberService();
FibonacciNumber port = service.getFibonacciNumberPort();
fibNo = port.fibNum(temp);

%>
<p>fib(<%= temp %>) = <%= fibNo %></p>
<a href = 'index.html'>Try another number</a>
</body>
</html>

Of course, clients should not see such messages displayed in the browser. Consider this error page more for the developer.

The web.xml deployment document is:

<?xml version = '1.0' encoding = 'UTF-8'?>
<web-app xmlns = 'http://java.sun.com/xml/ns/javaee'
xmlns:xsi = 'http://www.w3.org/2001/XMLSchema-instance'
xsi:schemaLocation = 'http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd'
version = '2.5'>
<error-page>
<exception-type>java.lang.NumberFormatException</exception-type>
<location>/errors.jsp</location>
</error-page>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
</web-app>

Any input to the HTML that is not a number will be caught and an error message will be displayed through the errors.jsp page.

Once we have all the files, we package them into a WAR:

jar cvf fibClient.war *.html *.jsp WEB-INF

and deploy it the same way as we did with fib.war.

For testing, open the http://localhost:8080/fibClient/ URL in your favorite browser.

Building a digital clock with the 8008 microprocessor

2009-07-27T16:37:00.006-04:00

Ever wondered how to design and build a clock on a Intel 8008 8 bit microprocessor? What logic is required? See Building an Intel 8008 Computer "Clock" for details on design, software, and hardware involved. My logic design skills are a bit rusty, maybe yours are better, so you will fully appreciate the insights.

Using Sound Waves in Brain Surgery

2009-07-21T18:54:00.007-04:00

A breakthrough approach to brain surgery that uses sound waves to destroy diseased tissues in your brain, thus avoiding opening the skull. From the article:

"The groundbreaking finding here is that you can make lesions deep in the brain--through the intact skull and skin--with extreme precision and accuracy and safety ... The ultrasound beams are focused on a specific point in the brain--the exact location depends on the condition being treated--that absorbs the energy and converts it to heat. This raises the temperature to about 130 degrees Fahrenheit and kills the cells in a region approximately 10 cubic millimeters in volume. The entire system is integrated with a magnetic resonance scanner, which allows neurosurgeons to make sure they target the correct piece of brain tissue"

Future tests will involve patients with Parkinson's disease.

You can read more details in the Technology Review.

Scripting in Android

2009-07-09T12:26:00.011-04:00

Damon Kohler released last month the Android Scripting Environment (ASE), which enables running Python scripts in Android. Access to location and sensors, activities and intents, phone calls and text messaging, are just a few examples of the APIs available to scripts.

A more detailed article on this topic can be found on the Motorola developer blog.

Google Chrome OS

2009-07-08T11:05:00.025-04:00

Back in December of 2008, I wrote about browsers replacing OSes. Google introduced the Chrome OS yesterday, "an open source, lightweight operating system that will initially be targeted at netbooks".

The OS targets speed, simplicity, and security. "We're designing the OS to be fast and lightweight, to start up and get you onto the web in a few seconds". It will run on x86 and ARM, and will run on a new windowing system on top of the Linux kernel.

In addition, Chrome OS is separate from Android; while Android was designed to run on mobile phones and set top boxes, Chrome OS was designed "for people who spend most of their time on the web, and is being designed to power computers ranging from small netbooks to full-size desktop systems".

Web application security flaws exposed

2009-06-11T14:16:00.043-04:00

Today I participated in the "Hacking 101" event hosted by IBM in Miami. It was a half day seminar, hands-on lab. Very interesting and useful I must admit. They talked about what are the top security issues of web applications today based on the OWASP Top 10 document. The interesting part is that they actually demonstrated some of the security issues discussed. In order to showcase everything, they have a test (fictive) web site set up, namely http://www.testfire.net/ (you can access it from your own station at will). Let me go through some vulnerabilities covered during the session.

Cross-Site Scripting (XSS) - Number 1 in the Top 10 list.

XSS is basically script embedded into HTML returned from a trusted site. One of the implications is that session tokens can be stolen. Let's see how:

First I search for the string 'Mihai', which will change the browser URL to http://www.testfire.net/search.aspx?txtSearch=mihai, printing the result like shown below:

Next step is to change the query string to http://www.testfire.net/search.aspx?txtSearch=<script>alert(document.cookie)</script>, resulting in information related to your session being made available:

So the cookie is available to JavaScript. How do we exploit this? First, you need the Tamper Data Mozilla add-on. Once you have it installed, open in by choosing Tools -> Tamper Data. Going back to Firefox, in the search text box enter %3Cscript%3Edocument.write('. Looking into the Tamper Data UI, you can locate the request just made to evilsite, and see that your cookie has been sent to it.

To exploit this vulnerability, one can send an email to the user with a link that has the above script embedded in it. Once the user clicks on it, the request will be sent to www.testfire.net, with the script as input for the search text box. When the script is echoed back to the application, it will be executed by the browser and the user cookies will be sent to evilsite.

SQL Injection - Number 2 in Top 10 list.

With SQL Injection, the user input is directly embedded into a SQL statement. One of the implications is that we can access data in a database. Let's say we wanted to log in as administrators into our dummy web site. First step is to get a sense of how the SQL statement is formed. For that, we enter a ' as the user name, followed by anything as password:

The result of trying to log in will be an error page that will display information related to how the SQL statement involving the user name and password is constructed:

Once we know how the query looks like, we can write in the user name field the text ' or 1=1--:

with the results of being signed in as admin:

Other security vulnerabilities were covered, such as Malicious File Execution, Insecure Direct Object Reference, Information Leakage and Improper Error Handling, and Failure to Restrict URL Access.

Of course, IBM has a tool called AppScan that can help in detect all the vulnerabilities I mentioned in this blog. How it works, in a nutshell, is by scaning your web application (i.e. website), identifying the security issues based on some test policies, pointing out the problems , logging the issues, and recommending fixes. Below is a screenshot of AppScan in action (taken from the pdf presentation slides):

If you want to find out more about the event, get the slides, try everything out, go to http://www.ibm.com/developerworks/offers/techbriefings/details/hacking.html.

All in all, a very informative session!

Top 5 smartphones for Q1 2009

2009-06-05T14:31:00.007-04:00

I was writing in one of my may posts about top most popular handsets in the U.S. at the end of 2008, new data come out (I read about it via cenriqueortiz) regarding top 5 smartphones sold in Q1 of 2009:

1. BlackBerry Curve
2. Apple iPhone 3G
3. BlackBerry Storm
4. BlackBerry Pearl
5. T-Mobile G1

Am glad to see the G1 up there. By the end of 2009, I predict it will move up to 4th or 3rd place.

And the winner is ... Xbox 360

2009-06-02T16:49:00.029-04:00

If you haven't heard about "Project Natal" don't feel bad, you have now! It is a body motion capture for the Xbox 360. There is no controller required (direct shot at Wii), by using a 'box' that can capture motion, sound, 3D movement for multiple users during a one game session, and offers facial recognition used for example for signing you in to Xbox Live. The release date, although not officially released, it is expected to be some time later this year (Christmas maybe?). I am curious about the cost of Natal. We should not forget that the Wii has a lower price compared to the Xbox 360 and PS3. I guess we'll find out sooner or later.

All the tools you need to work with JavaScript

2009-06-02T15:58:00.070-04:00

There is a JavaWorld article titled Ajax: Tools of the trade, which consists of a survey of tools for the JavaScript developer.

The article starts by mentioning the JavaScript support offered by popular IDEs such as NetBeans, IntelliJ, and Eclipse. It continues with describing tools such as Firebug (lets you edit, debug, and monitor JavaScript on the fly), YSlow (analysis webpages and suggests ways to imporve performance), and Hammerhead (measures the load time of web pages).

The next part of the article goes into ways of testing your JavaScript code, by using tools and frameworks such as JsUnit (unit testing framework for JavaScript), JSSpec (you have one or more tests that describe the behavior), YUI Test (testing framework for JavaScript), and Crosscheck (checks if your code runs in many different browsers).

If you are interested in testing your user interface, the article mentions some of the tools available, such as Selenium (set of tools that supports rapid development of test automation for web-based applications), Watir (an open-source library for automating web browsers), and YUI Test mentioned above which can also be used to simulate the DOM and user interaction.

Other utility tools for JavaScript include JSLint (JavaScript code quality tool), or JSMin ( removes comments and unnecessary whitespace from JavaScript files) and YUI Compressor (in addition to removing comments and whitespace, it also obfuscates local variables using the smallest possible variable name), for minimizing our JavaScript.

Since I have just started JavaScript, I cannot make any recommendations. Try them out, see which one fits your project best, and use it.

Free course on creating iPhone applications

2009-05-27T16:19:00.004-04:00

Stanford University offered a free iPhone application development training course. The course is available on iTunes U as video and pdf, and can be found on Standford on iTunes U website. Interesting is the fact that in only 7 weeks, the course has been downloaded a million times from iTunes U. You can read the press release for more information. If you are interesting in iPhone application development, then these resources should come in handy.

From HTML to XHTML

2009-05-20T11:21:00.039-04:00

XHTML, or eXtensible HTML, is considered to be the evolution of HTML. I believe that the biggest difference between these two is that XHTML is XML, while HTML is, well, HTML. Other noticeable differences are that XHTML can be extended to include new markup (i.e. elements for vector graphics are already available); XHTML is the language of choice for browsers on mobile devices; data written in XML can be easily transformed into XHTML. Do remember that XHTML is backwards compatible with HTML.

How to convert from HTML to XHTML:

- Change the DOCTYPE to (Strict) XHTML.  For example:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">

would become

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

- The <html> opening tag needs new attributes: xmlns, lang,
and xml:lang. For example:

<html>

would become

<html xmlns="http://www.w3.org/1999/xhtml" lang="en"
lang="en">

Why do we need both lang and xml:lang? Because depending on
how the XHTML is interpreted by the browser, either of them
might be needed, hence it is considered a best practice to
include both.

- There must be a matching closing tag for any opening tag.
This implies that if you have empty elements, the tag must
end with />. For example:

<br>

would become

<br />

Why do we need a space before the slash? Because older
browsers cannot recognize "/>" without that space.

- All elements must be in lowercase.
- Attribute values must be in between double quotes and have a
value.
- All special characters must be converted into entities.
For example:

& should be &amp;.

Parameterized types and bounded wildcards

2009-05-06T13:25:00.026-04:00

We know that parameterized types (in Java) are invariant, which implies that, for example, even though Integer is a subtype (subclass) of Number, List is not a subtype of List. Let's see how this impacts you code. Assume we have a class named Bucket declared below:

public class Bucket {
   public void add(E e){...};
   public void addAll(List list){
      for(E e : list) {
         add(e);
      }
   }
}

If you would try to do the following:

Bucket numberBucket = new Bucket();
List integers = new ArrayList();
...
numberBucket.addAll(integers);

you get the error:

The method addAll(List) in the type Bucket is not applicable for the arguments (List).

How can we get out of this? Easy, by using a bounded wildcard type:

public void addAll(List list){
   for(E e : list) {
      add(e);
   }
}

Top 10 most popular U.S. handsets in December 2008

2009-05-01T14:21:00.008-04:00

RCRWireless has published a while ago the top 10 most popular U.S. devices in December of 2008. Blackberry Bold and Blackberry Storm (which was released in November) came in at no. 6 and 3, while the iPhone still remains no. 2, but I assume these numbers are limited because of the single-carrier barrier. Topping the list was the Blackberry Curve.

Useful links for all mobile related

2009-05-01T12:28:00.003-04:00

mobiThinking has posted a very useful webpage of resources related to the mobile industry, covering news, blogs, guidelines, forums, and many many more valuable information resources. You can read more here.

10 Rules for Writing Safety Critical Code

2009-04-17T14:46:00.018-04:00

Gerard Holzmann's Ten Rules for Writing Safety Critical Code specifies rules for developing safety critical code in C, rules that improve software reliability and testability. More detailed descriptions can be found in the June 2006 Issue of IEEE Computer, which can be found here. For me, there are other programming languages out there who may be better suited for safety-critical (and real-time) systems, languages like Ada or Erlang. I believe that one important aspect of such systems is to make sure that the routines invoked will take a deterministic amount of time to complete.

Android and Symbian on Netbooks

2009-04-16T16:26:00.005-04:00

Corresponding to a report by In-Stat, HP is pushing Android into Netbooks. From the Information Alert:

"This solution bypasses the huge memory, storage, and graphics requirements associated with Windows and lowers hardware cost, as well as the software cost. It also addresses the changes in the market. Over the past decade, we've seen two megatrends in electronics – mobility and the Internet. As content and applications migrate to the Internet, these trends will change to mobile Internet and Internet ubiquity. Adopting Android or another open source OS with a custom UI and good browser technology addresses these changes in many specific applications and usage models."

I do agree with the article, and I believe that Android will have a bigger impact on non-smartphone devices (such as Netbooks) than it will have on smartphones.

Symbian is not behind on all this. According to this article, the S60 5th Edition runs on a "off the shelf Intel Atom based motherboard", which means directly on the x86 hardware. The difference is that Symbian runs on x86, while Android runs on ARM.

Visualizing Sorting Algorithms

2009-04-16T16:09:00.004-04:00

Here is a website where you can view animations of different sorting algorithms that shows you how they operate, how the preconditions affect the performance of the algorithms, and which one performs better than the other under certain conditions and input sizes. You can also view the source code behind each algorithm. If you are looking for other 'animations', you can find them here, here, here, and here.

Constant Interfaces

2009-04-15T11:56:00.018-04:00

A constant interface is one that contains no methods, only static final fields, each declaring a constant. Below is an example:

public interface UniversalConstants {
//Speed of light in m/s
static final int SPEED_OF_LIGHT = 299792458;

//Newtonian constant of gravitation in m^3 * kg^-1 * s^-2
static final double GRAVITATION = 6.6742867e-11;
}

There were times in the past that I've used such interfaces in classes that needed the constants. This is a poor use of interfaces. An interface serves as a type that tells you what a class that implements that interface can do with an instance of it. There is nothing of this kind when using constant interfaces. How can we avoid this? (At least) In two ways. One, define the constants inside your class, if you feel that there is a strong relationship between those constants and you class. The other way is to use a utility class that cannot be instantiated, like below:

public final class UniversalConstants {
//Speed of light in m/s
public static final int SPEED_OF_LIGHT = 299792458;

//Newtonian constant of gravitation in m^3 * kg^-1 * s^-2
public static final double GRAVITATION = 6.6742867e-11;
}

When using these constants from within your own class, you can add a static import declaration and you're done!

Android 1.5 (Cupcake) Highlights

2009-04-15T09:02:00.004-04:00

Android 1.5 introduces new and exciting features. Here are some that I find important:

Accelerometer-based application rotations
Faster Camera start-up and image capture
Much faster acquisition of GPS location (powered by SUPL AGPS)
Smoother page scrolling in Browser
Video recording and playback
Bluetooth: stereo bluetooth support (A2DP and AVCRP profiles), auto-pairing, improved handsfree experience
Browser: copy 'n paste in browser, search within a page
Framework for easier background/UI thread interaction
Raw audio recording and playback APIs
Support for using speech recognition libraries via Intent
LocationManager - Applications can get location change updates via Intent
Broadcast Intent for app update install succeeded - for smoother app upgrade experience

For a complete list of features, visit the android developers web page.

Breaking information hiding in Java

2009-03-22T09:34:00.010-04:00

Information hiding is one key feature of Java in particular, and OO in general. It is not to be confused with encapsulation, since you can bundle data with your methods and not hide it at all. Even though these two (information hiding and encapsulation) are different, they are usually used together by making the attributes of your class private data members and providing getter (accessor) and setter (mutator) methods to them. Having said that, let us look at an example:

public class InformationHiding {
   private Position position;

   public InformationHiding(double latitude, double longitude)
      throws IllegalArgumentException {
      //make sure you have proper values for latitude and longitude
      if (latitude >= -90 && latitude <=90 && longitude >= -180 && longitude <= 180) {
         throw new IllegalArgumentException();
      }
      position = new Position(latitude, longitude);
   }

   public Position getPosition() {
      return position;
   }
}

Can you spot the problem with this code (beside the lack of synchronization)? Let's see how we can break the check for proper values of latitude and longitude:

InformationHiding inf = new InformationHiding(45, 120);
Position pos = inf.getPosition();
pos.latitude = -100; //illegal value
pos.longitude = 240; //illegal value

How can that be? We did make the position data member private? The problem is that we returned a reference to that member. This is a common mistake. Even when you generate the getter method from inside our IDE (i.e. Eclipse), it returns a reference to the attribute, rather than a copy to it. How can we fix this? Easy, just return a copy of the data member:

public Position getPosition() {
   return new Position(position.latitude, position.longitude);
}

That's it! You could have used the clone method to make a copy of the object, but then some changes need to be made, like not implementing clone by using the constructor.

There are some cases when we do not need to return a copy of the data, namely when we deal with immutable objects (like Strings and the wrapper classes).

Android 1.1 and iPhone 3.0

2009-03-19T07:33:00.004-04:00

If you want a feature-by-feature comparison of Android and iPhone, read the Android Versus iPhone 3.0 article by lifehacker. Do remember that Android is only in its 1.1 release, while iPhone has seen its 3.0 version. Even though iPhone has more available features, let us not forget that Android is open source.

Smartphone sales numbers

2009-03-15T09:57:00.006-04:00

According to a Gartner report, smartphones sales grow by almost 14% compared to 2007. What is encouraging are the news regarding Android-based smartphones:

"Sales of Linux-based smartphones were up by 19 per cent year-over-year, mainly through Android-based smartphones being available through T-Mobile during the fourth quarter of 2008."

I expect this number to grow with upcoming Android-based smartphone models.

Top 25 Most Dangerous Programming Errors

2009-02-12T21:47:00.006-05:00

SANS Institute came out with a top 25 most dangerous programming errors, errors which can lead to serious security breaches.

"... experts from more than 30 US and international cyber security organizations jointly released the consensus list of the 25 most dangerous programming errors that lead to security bugs and that enable cyber espionage and cyber crime. Shockingly, most of these errors are not well understood by programmers; their avoidance is not widely taught by computer science programs; and their presence is frequently not tested by organizations developing software for sale."

Android Presentation

2009-02-10T20:17:00.004-05:00

Today I did a presentation to a group of students on Android, basically an overview of the platform. If you are interested, you can find the presentation here. Any comments are welcomed!

BOLT - the Java-based Browser

2009-01-22T08:15:00.022-05:00

What intrigued me about BOLT (which is in a beta version at the moment of this writing) is the fact that it is written in Java (Java ME). It is designed for entry-level phones (with MIDP 2.0 and CLDC 1.0 or higher), but certainly it runs just fine on smartphones too. It is considered to offer fast and secure web browsing. How secure? 128-bit SSL Connections, filtering done on the server to protect you from malicious code, certification error notifications, and pop-up blocker. How fast is it? Reports have mentioned that on a Nokia 6120 (which runs on the S60 platforms), BOLT loaded the phonearena.com website in 14 seconds, while the built-in browser loaded it in 40 seconds.

BOLT provides ECMA Script 262 JavaScript support (asynchronous java script will work) , but does not currently offer support for Java Applets. Data reductions and lower power consumptions are also achieved.

If you are looking for screenshots (and further test results), head to phonearena.

Top 5 Cellular Phone Producers for 2008

2009-01-22T08:00:00.004-05:00

Based on reports from PhoneArena, here is a list of the top 5 cellular phone producers in the global market for 2008:

Nokia - 470 million units sold.
Samsung - 200 million units sold.
LG - 100 million units sold.
Motorola - 99.9 million units sold.
Sony Ericsson - 96.6 million units sold.

I am still hoping Motorola will come through (eventually) and will revive its mobile devices unit. Until then, another 4000 jobs are expected to be lost (beside those 3000 from November of last year).

Related concepts from Android and Java ME

2009-01-13T10:23:00.079-05:00

I was thinking about the main components that provide the building blocks for your Android application, and on how they relate to similar concepts from the Java Micro Edition (Java ME) platform:

Activity. Activities in Android are the presentation layer for the application you are building. For each screen you have, their will be a matching Activity. Similar to this concept, in Java ME you have Forms (and more general maybe Screens). An Activity uses Views to build the user interface; similarly, a Form uses different items such as text fields, data fields, choice groups, etc. Generally speaking, in Java ME, on a Screen (or on a displayable), you can place a Canvas, an Alert, a List, a TextBox, and finally a Form. All these elements are used to build the graphical user interface for displaying information to the user and interacting with him by responding to the user actions.

Services. Services are those components that run in the background, and which do not interact with the user. They can update your data sources and Activities, and trigger specific notifications. I tried to think of a similar component in Java ME, but could not come with one. The only concepts I could think of was Threads and Timers (a way for threads to schedule tasks for execution in a background thread). The concept of Threads exists separately in Android also, hence such a comparison is not quite precise. Until background MIDlets are available with the upcoming of MIDP 3, I guess we do not have any other options.

Content Providers. They encapsulate data and provide it to your application, therefor acting as interfaces to the application databases. Sharing data across applications is achieved also by means of Content Providers. Such a concept is related to the RecordStores in Java ME, and more general, to the Record Management System (RMS - the persistent storage mechanism in Java ME).

Intents. Intents are a way of specifying what intentions you have in terms of a specific action being performed. Intents are mostly used for launching Activities. A similar concept in Java ME is described in the Broadcast Receivers section.

Broadcast Receivers. These components listen for broadcast Intents that match some defined filter criteria, and can automatically start your application as a response to an intent. Looking closely at the Intents and Broadcast Receivers components, for me, PushRegistry comes into mind. A PushRegistry is used to request a wakeup call from the implementation. What is important to understand about PushRegistry is the fact that they have a lifetime beyond that of a MIDlet. It is part of the MIDlet management software that runs on the device. When your MIDlet registers (at runtime or at install time) for push notifications, the device is obligated to listen incoming network connections and start your MIDlet if the appropriate connection has been made.

Notifications. Notifications let you signal the user by alerting him of an incoming event, and without using a separate Activity to achieve that. For example, you are monitoring the weather, and you want to be notified when a hurricane warning is in effect for your area (common in South Florida where I leave). This can be accomplished by adding Notifications to your weather monitoring system. In Java ME, one similarity would be the use of Alerts that inform the user about different events.

In later posts, I will describe more similarities between the two platforms at different levels. Stay tuned!

What will change everything?

2009-01-06T10:21:00.055-05:00

The Edge annual question for 2009, "what will change everything?", is being posed by John Brockman to a community of thinkers. More precisely, "what game-changing scientific ideas and developments do you expect to live to see?". Below are part of some answers that I particularly found interesting (although you should read all of them!):

Kevin Kelly, Editor-At-Large, Wired: "It is hard to imagine anything that would "change everything" as much as a cheap, powerful, ubiquitous artificial intelligence—the kind of synthetic mind that learns and improves itself."

Ed Regis, Science Writer: "The idea was that scientists and engineers would construct vast fleets of "assemblers," molecular-scale, programmable devices that would build objects of practically any arbitrary size and complexity, from the molecules up. Program the assemblers to put together an SUV, a sailboat, or a spacecraft, and they'd do it—automatically, and without human aid or intervention. Further, they'd do it using cheap, readily-available feedstock molecules as raw materials."

Marc D. Hauser, Psychologist and Biologist, Harvard University: "Science fiction writers traffic in a world that tries on possible worlds. What if, as in the Hollywood blockbuster Minority Report, we could read people's intentions before they act and thus preempt violence? An intentionality detector would be a terrific device to have, but talk about ethical nightmares. " This is something that I also thought about when thinking about the question posed.

Marcelo Gleiser, Appleton Professor of Natural Philosophy, Dartmouth College, talks about mastering death through. "I can think of two ways in which mortality can be tamed. One at the cellular level and the other through an integration of body with genetic, cognitive sciences, and cyber technology."

Freeman Dyson, Physicist, Institute of Advanced Studies: "I expect that genetics and molecular biology will be dominant for the next fifty years, and after that neurology will have its turn. Neurology will change the game of human life drastically, as soon as we develop the tools to observe and direct the activities of a human brain in detail from the outside". In a nutshell: direct communication between brain and brain.

Lawrence Krauss, Physicist, Director, Origins Initiative, Arizona State University: "The Use Of Nuclear Weapons Against A Civilian Population." To be honest, I doubt this will happen. Its implications are far too deep and serious.

Gregory Benford, Novelist, Co-founder & Chairman: "Live To 150." I second that!

Richard Foreman, Founder Director, Ontological-Hysteric Theater; Playwright: "Nothing Will Change Everything." Pretty straight forward, isn't it?

... and many many more. Definitely worth reading!

Top 10 Semantic Web Products of 2008

2008-12-25T13:06:00.016-05:00

ReadWriteWeb has posted an article on the 10 best Semantic Web products of 2008. The top two spots are taken by Yahoo and Microsoft. Yahoo! SearchMonkey is a search platform aiming at making the search better by leveraging web annotations. Microsoft acquired Powerset, a natural language processing search engine. Who has not made the list and maybe they should have: Twine by Radar Networks, which provides a new way of tracking, finding, and sharing content, all in one place.

Mobile Web Best Practices

2008-12-25T12:45:00.003-05:00

W3C has posted earlier this year some guidelines regarding mobile web best practices.

"This document specifies Best Practices for delivering Web content to mobile devices. The principal objective is to improve the user experience of the Web when accessed from such devices."

Most Popular Android Applications for November 2008

2008-12-15T12:25:00.008-05:00

FastCompany has published a post regarding the most popular Android Applications for November 2008:

SOURCE: fastcompany.com

OpenID into Browsers, Browsers repllace OSs

2008-12-06T20:06:00.020-05:00

A great post on O'Reilly Radar about getting OpenID into the browser. I find the idea fascinating: when you open your browser, it will ask you to unlock it by usign your OpenID information:

SOURCE: David Recordon on radar.oreilly.com

As you start surfing the web, the browser will take care of automatically logging you into any website. Furthermore, it will help you with the registration process. Why is this not yet implemented?

Another (future) innovation is described in an article from DesktopLinux entitled "Browser swallows OS": when you boot your computer, instead of an OS-based environment, you would get a browser-based environment, like shown below:

SOURCE: DesktopLinux.com

Fascinating, isn't it? The company that provides the browser operating system (called Cloud) is gOS. As Enrique Ortiz has also mentioned in his post, similar ideas have been tried in the past, but they all failed. Maybe this time it will be different.

Mapping open source to mobile

2008-12-06T19:15:00.004-05:00

VisionMobile published a report on the different open source technologies used in the mobile space, describing who is using open source, where they are using it, and how they are using it, a must read.

Semantic Web - Technology Maturity

2008-12-02T19:12:00.008-05:00

I recently read an article about the golden age of software architecture written by Mary Shaw and Paul Clements. They have a section on how technologies mature, therefore I thought about where the Semantic Web is on that six-phase scale. I believe that the Semantic Web lies at the end of stage four, moving towards stage five. Here is why:

- Basic Research: Basic ideas and concepts have been investigated. The structure of the Semantic Web has been defined, and the different layers have been identified and described into details.
- Concept formulation: There is a wide research community available, which has refined the concepts available in the Semantic Web, converging on a set of ideas and continuously refining the structure of it.
- Development and Extension: Preliminary applications of the Semantic Web have been spotted since a couple of years. One of the first such applications has been Dublin Core, a vocabulary for distributed Digital Libraries.
- Internal enhancement and exploration: Semantic Web has been extended to other domains, such as biology, and has been used for real problems such as a better way to integrate and combine data. In addition, specific companies offer training. The problem is that the tools are not yet quite there in terms of usability, in terms of making it easy for the user.
- External enhancement and exploration: The problem here is that a broader community of people who are not developers is not involved. There are not a lot of companies that use Semantic Web technologies. There is yet to be shown a substantial evidence of value and applicability. In my opinion, better known companies need to use Semantic Web. If you look at Ajax, the technologies behind it were known for a long time; but before Google Maps used it, it was not adopted in a broad manner.
- Popularization: There are commercial products that use Semantic Web; hence, the technology has been marketed.

In conclusion, even though part of phase five and six are available, there are incomplete. Without broader support, without better tools, without making it easier for the user to understand and use the technology, it will never become popular. Furthermore, even if we were to teach Semantic Web in Universities, it would make little difference because the industry needs also to adopt it more openly and frequently.

I would love to hear from somebody who has more experience with the Semantic Web and maybe a different view on where it lies in the six-phase system.

(Software) Agents and the Semantic Web

2008-11-19T14:12:00.014-05:00

I thought about why the concept of Agent has not taken off, why people/companies do not use them as widely as they use other technologies. Two reasons came in mind.

First, there is the security issue. How does one know that the software agent has not been tampered with, or that the information it caries is secure enough, or that other agents it meets are "good" agents, not "bad" ones. Since the concept of agent has to include the property of being autonomous, how can we restrict the agent in its actions and decisions without greatly reducing his autonomy?

Second, the job of an (software) agent is to talk to other systems, interpret and gather data, make decisions on that data, and present it back to the user in a readable and useful way.

While the first reason might have been already overcome, the second has not. In my opinion, to overcome this, one has to use the Semantic Web. If you add meaning to data, agents can interpret it and make proper decisions, without having to ask the user for guidance at every step (thus loosing its effectiveness, and some of the main properties it's supposed to posses, like being autonomous) . I am sure this is not an novel idea, and that people have already thought about it, but for me it makes sense. I envision an "Agent Store", or "Agent Market", where people would go and "rent" or "buy" agents to fulfill their immediate or long time needs, such as paying all utilities (power, phone, internet, cable, credit cards, etc), or scheduling a doctor appointment, etc.
Wouldn't this be nice?

Frequently Forgotten Fundamental Facts about Software Engineering

2008-11-18T20:53:00.006-05:00

Interesting article by Robert L. Glass, initially printed in 2001, vol. 18 of IEEE Software. The author writes about "forgotten fundamentals" facts regarding software engineering.

Self-Healing Hulls

2008-11-12T20:54:00.040-05:00

In the 2008 November issue of IEEE Spectrum, there is an article that talks about self-healing hulls. The carbon-fiber composition of a yacht can considerably heal itself after a collision. You can improve the healing process by inducing a little electric current. The work is being done by Eva Kirkby, a graduate student from EPFL. The main idea is that carbon-fiber is composed of carbon fibers and epoxy; the problem is that in case of impacts, these materials tend to separate internally causing cracks parallel to the surface of the material. In order to counter this problem, the material is infused with hundreds of very small bubbles filled with liquid-monomer molecules plus some small particles of catalyst. The outcome would be a hardening of the material. In order to keep the concentration and size of the bubbles to a minimum, Kirkby incorporated into the composition wires of a smart alloy, an alloy that can return to its initial shape after being deformed by applying heat (electricity) through it. Great idea!

Dilbert's self-aware comic strip

2008-11-12T17:10:00.009-05:00

In my recent posts I kept mentioning biologically-inspired concepts such as self-aware, self-healing etc. Here is a comic view of self-awareness:

I love it!

Do agile teams model or write documentation?

2008-11-10T21:33:00.032-05:00

To be honest, I had the misconception that agility and modeling are at the opposite poles, that agile teams right little or no documentation. That all changed once I read an article from Dr. Dobb's Journal. Some of the reasons agile teams do up-front modeling is "to answer questions around the scope that they're addressing, the relative cost and schedule, and what their technical strategy is." Another reason is to better grasp and manage the complexity of system architecture.

Some agile modeling an documentation best practices are mentioned as doing "some initial requirements and architecture envisioning early in the project to write executable specifications via a Test-Driven Development (TDD) approach, to single source information whenever possible, to write documentation later in the lifecycle, to promote active stakeholder participation, to implement requirements in priority order, to include modeling in iteration/sprint planning activities, to create models and documents that are just barely good enough for the situation at hand, to model storm the details on a just-in-time (JIT) basis, to sometimes model a bit ahead to explore complex requirements, and to take a multiview approach via multiple models".

One of the complaints that exist with using agile methodologies is that they cannot be applied on large-scale projects and in large development teams. For those kind of projects, plan-driven, model-based solutions are better suited. To achieve this kind of scalability, there is an agile version of Model Driven Development (where MDA is one example of it), called AMDD or Agile Model Driven Development. The difference is that instead of creating extensive models, you create instead agile models. Furthermore, with AMDD, you do just a little of modeling, followed by a lot of coding.

Controlled Chaos

2008-11-04T11:36:00.010-05:00

In the 2007 December issue of IEEE Spectrum entitled Controlled Chaos, the authors describe a new generation of algorithms based on concepts related to the thermodynamic concept of entropy, which is a measure of how disordered a system is. By the fact that malicious code changes the flow of data in the network, the entropy of the network is thus altered. The new malicious threat, called Storm, uses different ways to be installed on the host machine, mostly through email attachments. Hot do we protect the networks? First step is to know how the network traffic moves around the network. Such collections of data from nodes in the network are possible because routers or servers are configured in such a way as to provide information about the network traffic in form of source and destination IPs, source and destination port numbers, the size of the packet transmitted, and the time elapsed between packets. Information regarding the routers themselves is also collected. Such information is used by the proposed algorithms to build a profile of the network’s normal behavior. It is stressed that the entire network is monitored, not just one single link in the network.

The principle behind the entropy-based algorithms is the fact that "Malicious network anomalies are created by humans, so they must affect the natural "randomness" or entropy that normal traffic has when left to its own devices. Detecting these shifts in entropy in turn detects anomalous traffic." When the network has established patterns, any outcome that is different from the normal states of the network can be easily detected. Even if the malicious code manifests by downloading pictures from the internet, the fingerprint of the network would look unusual, different from what is expected, from how the network was used. The authors make an interesting point, namely that Internet traffic has both uniformity and randomness. A worm will alter both, making the traffic either more random, or more structured. In case of the 2004 Sasser attack, the information entropy associated with the destination IP addresses rises suddenly, indicating an increase in randomness in traffic destinations due to the scanning initiated by the infected machines, as it looks for new victims. At the same time, the entropy associated with the source IP addresses suddenly drops, indicating a decrease in randomness as the already infected computers initiate a higher than normal number of connections. The conclusion is that the network goes into a new internal state unknown before, hence easily detectable.

The Storm worm I mentioned at the beginning works in some perspective similar to other worms, namely new code is placed on the computer (because the user clicks on some attachment), which will make it to join a botnet. However, there are distinct differences between old warms and Storm. One of them is the way it makes the user click the attachment, like using a clever subject line for the email, or attachment name, related to hot topics that are currently on the news, such as elections, hurricanes, major storms, etc. Most importantly, Storm hides its network activity. It first looks what ports and protocols a user is using. If it finds a P2P program, such as eMule, Kazaa, BitComet etc, it will use that program’s port and protocol to do its network scanning. Storm will also look at what IP addresses the P2P program communicated with, and will communicate with them, instead of new IP addresses, which would trigger its detection. Furthermore, Storm will not spread as fast as it can, because it has a dormant and a walking mode. It will gather information for a short period, then it will go quit. Very interesting that Storm actually tailors its behavior based on the pattern of the network usage. How to detect Storm? The worm will still alter the network entropy. For example, during its active period, the host computer will send many emails, which is unusually for normal use. In addition, the port used is not 25. All these are hints that something is wrong inside the network.

A great article! Nothing short of what I am used to expect from IEEE Spectrum.

On System Design

2008-10-27T20:47:00.015-04:00

In an essay entitled "On System Design", Jim Waldo, a distinguished engineer with Sun Microsystems, expresses his ideas and opinions on system design, including factors that hinder the effort necessary to do system design.

Some of the techniques that aid in the process of good system design are Six Sigma, or UML. The latter helps in the development of good design, but it is you (as an individual or a team) that has to come up with the design. UML helps you in expressing that design better. Many approaches have been found to work, but there is no general approach that works on all projects. Depending on the project, you have to decide which approach better suites your needs. The only exception to this is given by Brooks, namely that good designs have one thing in common, that is they are produced by good designers. Jim Waldo explained this in terms of probability/statistics: those who have been able to produce a good design in the past are far more likely to produce a good design in the future. Furthermore, designers have to be bale to deal with ambiguity while creating the design, and to know that the question that cannot be answered right away, will be eventually answered at the appropriate time. The author mentions that instead of learning a process of design, it is better to learn how to best design. An indicative to the best way to learn how to design includes two factors:

1. Trying, failing, and then trying again.
2. Being under the guidance of someone who is an expert at the task.

It si the way of thinking that matters most in system design, rather than the subject that can be thought in a particular course. Interesting enough, the author mentions that System Design cannot be learned in one course, but should rather be though in a much larger process, similar to an apprenticeship. The relationship needed between a master and its apprentice is found at the graduate level, where each student has an adviser with whom he is involved in academic research. One other place is at work (in industry) where you get hands-on insight on system design. I would argue that at work, you are more constrained in terms of time; hence, there is less opportunity in learning system design.

Diversity in the sense of academic backgrounds (physics, philosophy, anthropology, computer science, music, etc), and how such a diversity creates different views on a given problem, is described as being beneficial. I would particularize this to software development in the sense of not trying to think of a solution for a problem in terms of a particular programming language, but instead design the solution independent of the software platform and only afterward think of what language can help me express this design the best (similar to the MDA concepts).

The problem with doing design up front is the fact that no immediate code is produced. The pressure to produce something that can be seen, or the measure of productivity by means of the number of lines of code written, still exists. What is needed is "an act of faith by management". He continues by saying that "if you find a manager who is actually willing to give you time to do the design task, stick with him or her. He or she is a treasure much rarer than gold."

The paper also mentions intellectual property (as a note on why system design is not shared among peers anymore), and how any patent has the same value as any other patent. For me this is unbelievable; it is equivalent to saying that ideas that are behind the pattern are the same, namely have the same value. The quality of an idea is not taken into consideration at all by the patent system. Furthermore, in case of a patent litigation, the jury is made up of ordinary (non-technical) people, not technical peers. Hence, "it is very hard to learn about good system design unless you can see and study other system designs, both good and bad. The intellectual property atmosphere in industry has limited the number of designs that are actually talked about, and has convinced many system designers that they should not even look at the designs that are available."

Ways of solving the lack of system design from academia and industry are given in forms of agile methodologies and open source projects, because they enhance the discussion of a system's design in several ways: the communication between two (or a small group) of programmers can help in clarifying and better understanding the design of a system; furthermore, communicating the design to other members of an open source project will help clarify the design of a system. It is interesting to note that the author provides a different view to both agile methodologies and open source projects, namely them being a reaction to the impossibility of doing system design in academia and in the industry. Overall, the paper makes for an inspiring reading. You find yourself nodding and agreeing with the statements made while reading the essay.

Images of the Sun

2008-10-17T16:55:00.003-04:00

The Boston Globe has a series of amazing images of the Sun. Enjoy!

Why is self-healing in computer systems important?

2008-10-14T20:44:00.034-04:00

Reading about the malfunction that rendered the Hubble Space Telescope silent, I realized indeed how important is for systems to have the property of self-healing that our human body has, and in the broader sense, be autonomic. This would imply for the system to know itself in such a way as to poses detail knowledge of its components, status, and internal and external connections. If a system does not have information about a specific component, it cannot control it, hence the importance of knowing itself.

Furthermore, reconfiguring itself based on the environment is also a desired property. Most importantly, such a system would need to heal itself without the interference of human experts. Why do we need such a self-healing characteristic in computer systems? The Hubble Space Telescope mentioned above is one example. The failure in the telescope came from a unit that collects data and transmits it to earth. Solving this problem means to remotely send commands to the telescope to switch its operations to a backup unit. Why hasn't this been achieved automatically? Because Hubble was not designed with self-healing in mind. Would have been that complicated to discover the problem on its own and find an alternative resource that it could use to continue its normal operation? Self-healing really means just making use of redundant or underutilized components to take over the task of the malfunctioned element. This is similar to how the brain works when parts of it are damaged. The problem is that because Hubble is not 'aware' of its backup unit, that specific unit has not been utilized since 1990, making it subject to "harmful rays of the sun, extreme temperature changes during orbits and 18 years of cosmic debris".

If you are interested in Autonomic Computing, IBM has a whole research project devoted to this subject. You can find out more about this here.

Linearity and Nonlinearity in Biology, Computer Science and the Financial Market

2008-10-06T15:38:00.084-04:00

One of the questions that I have, inspired by one of the graduate classes taught by Dr. Ravi Shankar at FAU, is can we exploit the biological architectures to come up with improved computer architecture, both software and hardware. One aspect that rose my interest was the nonlinearity of different biological systems, and if we have such examples of nonlinearity in computer science. In ecological systems, we have Robert May's bifurcation diagram shown below:

SOURCE: https://ccrma.stanford.edu/~blackrse/LogisticMap_BifurcationDiagram.png

If the population growth factor equals to 4, the population jumps around in a chaotic, nonlinear manner. The main idea of the bifurcation diagram is to be able to see the successive period doubling which take us into chaos. We have such bifurcation, such branching, in the blood vessels, as well as in the air vessels. Now for the blood vessels, they can expand to adapt the blood flow. Let us denote the internal pressure, the pressure across the walls, with P, and the volume inside with V. Plotting this system we get the figure below:

What we get is a deterministic nonlinear system. The upper part of the slope is around 100 times the lower part. In case of a disease, like arteriosclerosis where you loose elasticity and you get a higher blood pressure, or in the case where you have more elasticity hence you have a higher pressure, you get a more linear system:

The blood vessels system functions properly only in the nonlinear case. Both linear cases have a negative impact. Do we have such linearity in system development? In software development process, the Waterfall model is the only model that has this linearity property:

The waterfall model is argued to be considered a bad practice mainly because it is impossible to 100% complete one phase before moving to another. When using such a model, it is implied that there are no changes in the requirements, problems can be fully predicted, and the design is correct before the implementation phase starts. Any other development process models do not exhibit the linearity property, but are rather nonlinear. Let us take the spiral model for example, shown below:

Spiral model (Boehm, 1988)

The diagram above can be viewed as a fractal, which is an example of a nonlinear system. Another model that expresses nonlinearity is the iterative and incremental one that is an essential or general part of other models such as RUP, Extreme Programming, Agile Software Development:

The iterative and incremental approach has been developed in response to the linear waterfall model. The nonlinearity characteristic is necessary in order for these models to display the property of adaptability to change, redesign, and learning from other iterations.

If we look at the DOW Jones Industrial Average for 2008, we can see some characteristics of chaos (another manifestation of nonlinearity) depicted in the shaded blue rectangle, that would predict the continuous fall starting with the beginning of October:

SOURCE: Yahoo! Finance

Nonlinearity is present throughout this graph, but chaos really sets in when the rate of the index goes up and down by a much higher rate than it did in the past. The high change in the DJI over a small period of time is a characteristic of chaos behavior. This is also seen if we look at the volume indicator below that plots the number of shares traded during that period of time:

SOURCE: Yahoo! Finance

From September 12 to September 19, there is an almost 50% increase in the number of shares traded. Between September 19 and September 25, there is around 50% decrease in the number of shares traded. Such a high increase and decrease in a two week period is chaotic and uncontrolled, and it is not seen anywhere in the graph for the past year. Having said that, we could certainly look for such chaotic manifestation in the future to better predict the market.

As a conclusion, we have seen several examples where nonlinearity in the form of fractals and chaos is useful and beneficial. Thinking in such terms will have a positive impact in domains ranging form computer science to financial systems.

Nokia unveils "Comes With Music"

2008-10-03T11:09:00.011-04:00

From Nokia's Press Release:

"The company announced Nokia Comes With Music, a revolutionary program that enables people to buy a Nokia device with a year of unlimited access to millions of tracks from a range of great artists - past, present and future. Once the year is complete, customers can keep all their music without having to worry about it disappearing when their subscription is over."

The CEO of UMG International was with Nokia to launch the program. "It's fantastic to work with Nokia on Comes With Music," said Grainge. "We feel it's an innovative way for people to discover and enjoy new artists, while at the same time having access to the amazing depth of the Universal catalog. Comes With Music allows our artists to reach new audiences in a very easy and affordable way.""

Google's Project 10 to the 100th

2008-09-24T21:43:00.015-04:00

Project 10 to the 100th is a call for ideas that have an impact on the entire world, affecting as many people as possible. You have until October 20th, 2008 to submit your idea. From the top 100 ideas, you have a chance to choose the 20 semi-finalists. In the end, up to 5 ideas will be selected, and Google is committing $10 million to implement those ideas.

It is important to understand that you will not receive the money, but rather a Request for Proposal process will begin "to identify the organization(s) and proposals that are in the best position to help implement the selected ideas". Hence if you wanted to participate in this project for the money, then you are misunderstanding the scope of it. In terms of Google, you "get good karma and the satisfaction of knowing that your idea might truly help a lot of people".

JNI Example

2008-09-19T16:33:00.082-04:00

JNI stands for Java Native Interface, which allows you to use, inside your Java application, code written in other programming languages. I will walk you through an example (developed under Windows) of using JNI.

Here are the main steps we need to follow:
- Create a java application that declares the native method.
- Compile the program.
- Generate the header file using javah.
- Implement the native code inside a C application.
- Compile the C code and generate the native library (dll).
- Run the java program.

Let us go through each of these steps:

1. Create a java application that declares the native method.


/**
* Shows a simple example of using JNI
*/
public class JNIExample {
  //Declare native method
  private native void displayMessage();

  public static void main(String[] args) {
      //Load native library
      System.loadLibrary("JNIExample");
      //Call the native method
      new JNIExample().displayMessage();
  }
}

2. Compile the program.
javac JNIExample.java

3. Generate the header file using javah.
javah -jni JNIExample

4. Implement the native code inside a C application.


#include 
#include 
#include "JNIExample.h"

JNIEXPORT void JNICALL Java_JNIExample_displayMessage
(JNIEnv *lEnv, jobject lObj) {
  printf("This is a JNI Example!\n");
  return;
}

The method signature matches exactly the one from the JNIExample.h header file.

5. Compile the C code and generate the native library (dll).
Open a Visual Studio (or similar) command prompt. In my case, it was located under "start->Programs->Visual C++ 2005 Express Edition->Visual Studio Tools->Visual Studio 2005 Command Prompt".
Run the command from the directory where you have the JNIExample.c file:
"cl -I"c:\Program Files\Java\jdk1.5.0_08\include" -I"c:\Program Files\Java\jdk1.5.0_08\include\win32" -MD -LD JNIExample.c -FeJNIExample.dll". Your path to the include directory might be different, so make sure you adjust that according to your settings. The -LD option makes sure that the compiler generates a DLL file. The -MD option makes sure that the DLL generated is linked with the win32 multithreaded C library.

6. Run the Java program.
java JNIExample

Some problems I ran into it while testing the code:
- I was missing the msvcr80.dll file, so I downloaded from here and copied it to c:\windows\system32 directory.
- Even though a manifest file was created, I hade to embedd it inside the dll. I have used the following link to solve the problem: http://msdn.microsoft.com/en-us/library/ms235591(VS.80).aspx. Here is the command: "mt.exe -manifest JNIExample.dll.manifest -outputresource:JNIExample.dll;2"

Microsoft joins OMG

2008-09-13T23:00:00.020-04:00

On September 10th, Microsoft announced its membership in the standards body of OMG (Object Management Group). This does not imply that Microsoft is moving away from its DSL (Domain Specific Language) strategy, where the DSL Toolkit ships with the Visual Studio SDK. What Microsoft is doing is actually supporting both DSL and UML, providing you with the chance to choose the right approach for the right job.

From the press release:

“We’re building modeling in as a core part of the platform,” said Bob Muglia, senior vice president, Server and Tools Business at Microsoft. “This enables IT pros to specify their business needs and build applications that work directly from those specifications. It also brings together the different stages of the IT life cycle — connecting business analysts, who specify requirements, with system architects, who design the solution, with developers, who build the applications, and with operations experts, who deploy and maintain the applications. Ultimately, this means IT pros can innovate and respond faster to the needs of their business.”

"Accept cookies from sites" remains unchecked in Forefox

2008-09-11T21:25:00.024-04:00

In Firefox, something strange started to happen today. Trying to access iGoogle and Yahoo! Mail, they kept telling me that my browser does not accept cookies. How is that possible? I checked my Privacy settings, and there it was, my "Accept cookies from sites" option was not checked. How did that happen? I don't remember unchecking it. No problem, I checked it and started reading my Technology news from iGoogle and checking my email. Some time afterward, guess what? Same problem! Now, I am concerned. I'm thinking my browser is being exploited somehow. But something does not make sense here. By not accepting cookies, I'm actually restricting access, not giving access, I'm increasing my privacy, not decreasing it. OK, so I'm not being exploited, I'm not revealing any private information through my browser, but at the same time, the cookies option somehow gets unchecked. Without keeping you into suspense for much too long, the problem was with one of my browser extensions, Stealther, namely it was being used. To be honest, I do not remember starting it (checking it under Tools -> Stealther), but that my friends, is another story.

BlackBerry Flip and IBM's Spoken Web

2008-09-11T09:36:00.015-04:00

RIM introduced the first BlackBerry Perl Flip 8220 smartphone. The official website for the phone can be found here. Taken from the RIM press release:

"The quad-band EDGE based BlackBerry Pearl Flip smartphone presents a sophisticated look with a sleek design and a chrome-finished frame surrounding its smooth, luminescent face. Packed with an abundance of powerful features, it weighs only 3.6 ounces and measures approximately 3.9” x 1.9” x 0.7”. Featuring two high-resolution, light-sensing color displays, the external LCD makes it easy to preview incoming emails, text messages and phone calls without opening the handset, while the large, 240 x 320 internal LCD displays messages, videos and web pages with impressive detail and contrast.

“The popularity of BlackBerry smartphones has grown tremendously around the world and the introduction of this exciting new flip phone will help extend the reach of the BlackBerry platform even further,” said Mike Lazaridis, President and Co-CEO, Research In Motion. “The BlackBerry Pearl Flip is a full-featured smartphone with a unique and friendly design and it is a natural choice for flip phone users who want to start doing more with their phone than just talk.”"

Voice quality is assured through the use of Speaker Independent Voice Recognition (SIVR) for Voice Activated Dialing (VAD). It includes "support for mp3 ring tones, smart dialing, conference calling, speed dialing, call forwarding, voicemail attachment playback and enhanced background noise cancellation. It also features a speakerphone and Bluetooth® 2.0 for use with hands-free headsets, stereo headsets, car kits and other Bluetooth peripherals such as a GPS receiver. The removable/rechargeable 900 mAhr battery provides four hours of talk time and over 14 days of standby time".

IBM is testing a voice-based web browser, developed under the "Spoken Web" project of IBM's India Research Laboratory. Some of the technologies used are Voice eXtensible Markup Language (VoiceXML) and HyperSpeech Transfer Protocol (HSTP). You can read more about it here.

12 Sly Web Tricks That Put You in Control

2008-08-27T16:05:00.008-04:00

Great article on PC World about 12 Sly Web Tricks That Put You in Control. You find out how you can Turn Wi-Fi Thieves' Worlds Upside Down (literally), Make a Laptop Thief Regret It, Finding out if the email you sent was read or not, Send a Self-Destructing Email, and other similar (and sometimes very useful) information.

Basic Set operations in Java

2008-08-26T18:23:00.071-04:00

How do we work with Sets in Java when it comes to performing the basic operations: Union, Intersection, Subset, Complement, Cartesian Product (for which there is no standard Java method in the Set Interface)? Do we have some kind of a collection that maps this mathematical concept into Java? Yes we do.

The Set Interface models the mathematical concept of a set and it is a Collection that contains no duplicate objects. Before talking about the specific methods that we will use, you must be aware of the three most used Set implementations: HashSet (uses a hash table to store its elements), LinkedHashSet (HashSet that also maintains a doubly-linked list running through all of its entries), and TreeSet (a sorted set).

Assume we have two sets s1 and s2. Going back to the basic set operations, we have:
- Union: the union of sets s1 and s2 is a set whose elements are contained in either set s1 or s2.


Java: s1.addAll(s2) - adds all elements from s2
 in s1 if they are not already present.

- Intersection: the intersection of two sets s1 and s2 is a set whose elements are in both s1 and s2.

 
Java: s1.retainAll(s2) - s1 becomes the intersection of
 s1 and s2.

- Subset: s2 is a subset of s1 if all elements of s2 are also elements of s1.


Java: s1.containsAll(s2) - returns true if s1 contains
 all of the elements of s2.

- Complement: the complement of s2 in s1, denoted s1 - s2, is a set of all elements that are members of s1 but not of s2.


Java: s1.removeAll(s2) - removes from s1 all the
 elements that are also contained in s2.

- Cartesian Products: the Cartesian product of two sets s1 and s2 is the set of all ordered pairs (x, y), where x is an element in s1, and y is an element in s2.


Java: public static Set computeCartesianProduct(Set s1,
Set s2) {
    Set result = null;
    if (s1 == null || s2 == null) {
        throw new IllegalArgumentException();
    }
    if (s1.isEmpty()) {
        return s2;
    }
    if (s2.isEmpty()) {
        return s1;
    }

    result = new HashSet();
    for (Object obj1 : s1) {
        for (Object obj2 : s2) {
            result.add("(" + obj1 + "," + obj2 + ")");
        }
    }

    return result;
}

UPDATE (04/30/09): For the Cartesian Product operation above, I have used a raw type for unknown set element type. As of Java 1.5, you should consider using generics. For example, you should use an unbounded wildcard type for the input parameters of the computeCartesianProduct method, making the above code type safe and more flexible. This implies that instead of using the declaration Set s1, you should actually have Set<?> s1.

Sun Certified Java Programmer (SCJP) Exam

2008-08-22T16:43:00.015-04:00

Today, I passed the Sun Certified Java Programmer (SCJP 1.5) exam. Throughout this post, I will share my experience preparing for it.

Before I get started, a little bit of background. I started developing in Java in 2001 (second year of college). Most of the software I have written was using the standard and mobile editions of the Java Platform. I have some knowledge of the enterprise world of Java, but mostly through Servlets and JSPs than anything else. In addition, I took a 6-months Java tutorial back in 2005 that covered OO Topics and Java Core (everything up to concurrency), Java Advanced (concurrency, networking, RMI, JDBC, XML) and Java Enterprise (Servlets, JSP, Custom Tags, JMS, EJB). Hence, I was not knew to this technology when I first started preparing for the SCJP exam in mid June (I also became a SCJA in January this year).

First step was to find a study book. This was not hard since I already knew about the SCJP for Java 5 Study Guide from Sierra and Bates (I already had the 1.4 version of the book). This is an excellent material, no doubt about it. It has a complete coverage of the exam objectives, examples, exercises, exam watches, basically anything you would possibly want from a certification book. Highly recommend it. I only went through this book once, done most of the exercises, and took the free practice exam that comes with the CD (you also get a bonus MasterExam practice test). Once I indentified my weaknesses, I went over again through the specific chapters in the book. At the end, I took the MasterExam practice test and did a little better. How many times you read the book really depends on you, on how familiar you are with Java, on how fast you graps the topics detailed there. I read about people who read the books as many as five times. If you think it helps, and you have time, it is up to you!
Now I have to mention that the two practice tests were the hardest from all the test that I have done afterwards, harder than the exam, hence if you nail these tests, the real exam will feel much easier. It might be harder also because, like other practice tests I took, when you get a multiple-choice question, they don't specify how many correct answers you have, while the real exam, and some of the other test, does. I understood the reason why it is not specified, but I would have wanted an option from where to choose if I should be given, or not, the number of correct answers.

Next step, a combination of taking many mock exams, and reading online SCJP notes. The best place to go for this is to the Java Ranch SCJP Forum webpage. How much it helped me? Enormous! Beside the benefit of having a forum specifically dedicated for SCJP, you get links to basically anything that you might want (and need) for this exam, such as faq, notes, mock exams, etc. Such a pool of resources gathered under one roof is almost impossible to find. Two thumbs up for everybody involved there!

If you want commercial practice tests, I would suggest Whizlabs, uCertify, Sun's own ePractice Certification Exam. From what I read, and from my own experience, I would say that Whizlabs is harder than any practice exams I know (except the one from the book). It contains tips, study notes, and 4 practice exams - best overall preparation kit. uCertify is a bit easier than the real exam, and it contained minor software errors, but was a good resource in the end. Bundled in it come 7 tests, tips, notes, etc . Sun's web-based practice exam came the closest to how the real exam was (which kind of makes sense, I know). This is the main reason I bough it. The score that I got form the third (and last) practice test was the one I got in the real exam.

Going through many mock exams and practice tests, I started writing my own SCJP Notes document. It contains everything that I thought was essential for the exam (inspired from the book and many existing online notes), together with things I have missed at tests (my own weaknesses if you like). You can read the document here.

As for the exam itself, you get 210 minutes (I was done in around 130 minutes). Honestly, I thought I would do worse than I did. I was unsure on some of the answers I had given, but when you take so many mock and practice exams, when you read from the many resources available out there, you have to start trusting your guts. And this is mostly true on API related questions, i.e. does the reverse method exist in both String and StringBuffer classes? What about replace? Java 1.5 specific questions (topics not present on older versions of Java) were on the exam quite often (such as generics, autoboxing, varags, etc). The Thread-related questions were harder than I expected, and I did the worse on that section than I did on any other (only 75%). In the practice exams, threads were one of my strongest suites. If you aks me, Concurrency, Generics and Collections are the hardest topics around.

What can I say more? Good luck to any of you who want to take this exam, and if you have any questions, drop me a comment.

Cell Phones - Top 3 best sellers

2008-08-19T21:57:00.012-04:00

I remember reading about it a while ago. Digging a little through the Internet, I found the source in engadget. Here are the facts:

Nokia 1100 - around 200 million units sold.
Motorola RAZR V3 - around 50 million units sold (although I believe that the Motorola StarTac sold more units).
LG Chocolate - around 10 million units sold.

Now, Apple's iPhone has a big chance of overrunning the third spot by the end of 2008 (with the new improved and cheaper 3G model). We'll just have to wait and see. Of course, searching the internet will reveal a different top for the most selling cell phones.

On a similar note, CNET has published a review on the best 5 cell phones. Why haven't I owned any of them yet?

DimDim 4.0 Released

2008-08-09T02:51:00.006-04:00

DimDim, a free web conferencing service, has launched version 4.0. Some of the key features added were:

Recording: You can now record your meetings and share playback URLs or embed the recording directly onto your own website just like YouTube videos.
Multiple Presenters: With a single click you can allow any attendee to share their presentation, whiteboard, webcam - even their desktop.
Mac Desktop Sharing: Mac users can share their desktop with anyone using just a browser.
Free Teleconferencing: With the improved free VoIP microphone sharing everyone now gets their own unlimited free conference call account.
Private Meetings: Simply assign a meeting key and only those who know both your meeting room name and your meeting key will be able to join.
No Install: Now you don't need to install anything to join or even host a meeting. You'll only need to install our screen casting plug-in if you choose to share your desktop.

Web Design - Scalability and Speed

2008-08-07T04:30:00.006-04:00

Greg Linden reported that every 500ms of latency costs Google 20% of its traffic. Similarly, every 100ms of latency costs Amazon 1% of their sales. The presentation concludes that speed matters (big time), but it is hard to achieve high speeds when you are manipulating large data. Here is where a scalable design matters. My experience with web design is minimal. Maybe you have some good feedback/tutorials/articles on how to achieve scalability when large amounts of data is involved.

Open Web Foundation

2008-07-29T12:07:00.007-04:00

Several days ago, the Open Web Foundation has been created. From the official announcement:

"The Open Web Foundation is an attempt to create a home for community-driven specifications. Following the open source model similar to the Apache Software Foundation, the foundation is aimed at building a lightweight framework to help communities deal with the legal requirements necessary to create successful and widely adopted specification."

You can also find a brief presentation on the announcement web page mentioned above. Some of the companies that support the efforts of the foundation are Facebook, Google, O'Reilly, Sourceforge, Yahoo, and many other.