Making java method arguments as final

Question

What difference that final makes between the code below. Is there any advantage in declaring the arguments as final.

public String changeTimezone( Timestamp stamp, Timezone fTz, Timezone toTz){       return .... }  public String changeTimezone(final Timestamp stamp, final Timezone fTz,          final Timezone toTz){     return .... } 

Answer 1

As a formal method parameter is a local variable, you can access them from inner anonymous classes only if they are declared as final.

This saves you from declaring another local final variable in the method body:

 void m(final int param) {         new Thread(new Runnable() {             public void run() {                 System.err.println(param);             }         }).start();     } 

Answer 2

Extract from The final word on the final keyword

Final Parameters

The following sample declares final parameters:

public void doSomething(final int i, final int j) {   // cannot change the value of i or j here...   // any change would be visible only inside the method... } 

final is used here to ensure the two indexes i and j won't accidentally be reset by the method. It's a handy way to protect against an insidious bug that erroneously changes the value of your parameters. Generally speaking, short methods are a better way to protect from this class of errors, but final parameters can be a useful addition to your coding style.

Note that final parameters are not considered part of the method signature, and are ignored by the compiler when resolving method calls. Parameters can be declared final (or not) with no influence on how the method is overriden.