Category: Java

What happens if you write something like a = a++ in Java?

Posted: 2006-09-13   |   Categories: Java, Programming

I often happened to see discussions about this topic. Basically, here is the question. If you have such a code:

   
int a = 0;
a = a++;
System.out.println(a);

What does it print?

More than 50% of the programmers will answer 1, some of the remaining will say “I don’t know” and the others will say 0. Well “the others” are right!

Provided that such a code MUST NEVER BE WRITTEN, let’s try to understand, for academic purposes, why it prints 0.

POJO (Plain Old Java Object): The simpler...the better.

Posted: 2006-08-21   |   Categories: Java, Programming   |   Tags: POJO

A POJO is simply an object built using a Java class that does not implement any special interfaces such as those defined by the EJB 2 framework. An example of a POJO is a class composed by only:

1. Properties, representing the object’s state.
2. Getter and setter methods for the properties.
3. Business methods, representing behaviour.

Some properties can represent associations with other POJOs. Here is an example of implementation of the Person entity using a POJO:

How to force one or more metacharacters to be treated as ordinary characters in a Java Regular Expression (RegEx)

Posted: 2006-07-12   |   Categories: Java, Programming   |   Tags: Metacharacter, RegExp

When using RegEx in Java you might face the need of treating one or more metacharacters as ordinary characters. As a reminder the metacharacters in a Java RegEx are:

([{^$|)?*+.

If you want to treat them as ordinary characters you have two options:

1. Escape the metacharacter with a backslash,
2. Enclose the whole string that contains metacharacters within Q and E

Q means: “quotes all characters until E”, while E ends the quotes.

Using proguard obfuscator through the Wireless Toolkit

Posted: 2006-06-20   |   Categories: Java, Programming   |   Tags: J2ME, Java ME

When you develop an application you might want to protect your code. A good way to accomplish this is using obfuscation. Proguard is a good open-source tool you can use for this purpose. To use it through the Wireless Toolkit (WTK), after downloading Proguard, you need to tell the WTK where it can find the obfuscator. You can do that by editing the file ktools.properties that you can find under %WTK%wtklibWindows, where %WTK% is the root directory of the Wireless Toolkit. Basically, you just need to add the two following lines to the aforementioned file: