The final modifier indicates that a data field cannot be modified, as in

    final double PI = 3.14;

Any attempt to assigne PI to a new value will result in a runtime error. Thus final makes data useful as constants.

Often such constants are needed by other classes, so they are declared static as well, as in

  public class MyMath
  {
    public final static double TWO_PI = 6.28;
    ...
  }

Then other classes can then reference it, as in

    ...
    double y = theta / MyMath.TWO_PI;
    ...

final Methods

The final modifier is also used with methods to indicate that they cannot be overriden by subclasses.

  public class MyMath
  {
    ...
    public final double MyFormula() {
      ...
    }
  }

This helps to improve their performance since the JVM will not need to check for overriding versions with the method is invoked.

Latest update: Oct. 22, 2004