When to use final keyword

Description

A final variable cannot be modified. You must initialize a final variable when it is declared. A final variable is essentially a constant.

Final variables

 
public class Main {
  final int FILE_NEW = 1;
  final int FILE_OPEN = 2;
}

Prevent overriding

Methods declared as final cannot be overridden.

 
class Base {/*from   w ww  .  j  ava  2  s  .  c  o  m*/
  final void meth() {
    System.out.println("This is a final method.");
  }
}

class B extends A {
  void meth() { // ERROR! Can't override.

    System.out.println("Illegal!");

  }
}

If you try to compile the code above, the following error will be generated by the compiler.