final variables

A final variable cannot be modified.

You must initialize a final variable when it is declared. A final variable is essentially a constant.

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

Using final to Prevent Overriding

Methods declared as final cannot be overridden.

 
class Base {
  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.

D:\>javac Main.java
Main.java:7: cannot find symbol
symbol: class A
class B extends A {
                ^
1 error