This was a fun, if particularly stupid, one:

public void method check(int value){
  if(this.x == value)
  {
    //do whatever
  }
}

the previous works as long as x and value are small, but not when they are big. Why? Because x is an Integer not an int. Java helpfully autoboxes the int by building an Integer and then does a pointer comparison. This still works for small numbers because java caches the lower Integer constants rather than creating them on the fly all the time so new Integer(value) actually resolves to the same object as x, but once the number gets big enough Java has to create a new object and then suddenly the comparison fails.

I actually don’t blame autoboxing for this one. Autoboxing was a good idea. Having == mean pointer equality (or really fundamental type equality) rather than actual equality combined with not modeling all fundamental types as objects was not such a hot move.

A co-worker of mine recently made the comment that a lot of times you see Java code using inheritance where composition is a much better solution. This is very true and worth pointing out.
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I thought this was interesting… In Java, a block scoped variable may conflict with a local variable declared later in method scope, but not previously (as shown below):

class A{
  public static void main(String args[]){
    {int k = 5;}
    int k = 12; //this is OK
    {int k = 22;}//this is not....
  }
}

This is not the same as C++ where this compiles happily:

int main(){
  {int i;}
  int i;
  {int i;}
  return 0;
}

Usually C++ has the more obscure behavior….

I just noticed that java enums allow protected member variables and methods. Why is this interesting? Can you think of any code that might actually make use of a protected member in an enum (as opposed to private)? Example after the jump (warning, not practical…).
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Providing a robust, maintainable, and interactive interface to your C/C++ application can be a challenge, but I’ve found that a combination of SWIG, Java, and JRuby (or Jython if you prefer) makes for a very powerful combination.
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DVSL is a fairly small, little known, product associated with the Velocity project over at Apache which takes the best part of XSLT: XPATH, and replaces the verbose and frustrating scripting of XSLT with a java-based template language instead.
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Rhino is a JavaScript/ECMAscript implementation in Java. Using the new java1.6 scripting API you can now easily embed JavaScript into your Java applications. I thought I’d try writing yet another implementation of the net_tool application using Rhino. Originally this was going to be a single article, but it turns out to be a two-fer.
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So apparently the hex to binary in 4 languages portion of this web page is what gets the most google hits and who am I to argue? So without further ado, hex to binary in Java as well…

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Most people are aware of java annotations by now, but I’m not sure everyone knows about @Override. They really should.

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If you want to parse a custom language in java then Javacc is your tool. At the moment this is probably more a reminder to myself than a great article for anyone else to read, but as you find it useful feel free to take a look. More after the link…
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