Why should I use the keyword “final” on a method parameter in Java?

Sometimes its nice to be explicit(for readability) that the variable doesn't change. Here's a simple example where using final can save some possible headaches

public void setTest(String test) {
    test = test;
}
if you forget the 'this' keyword on a setter the variable you want to set doesn't get set. However if you used the final keyword on the parameter then the bug would be caught at compile time.

http://stackoverflow.com/questions/500508/why-should-i-use-the-keyword-final-on-a-method-parameter-in-java