A browser with JavaScript enabled is required for this page to operate properly.
Trail: Learning the Java Language
Lesson: Interfaces and Inheritance
Section: Inheritance
Writing Final Classes and Methods
Home Page > Learning the Java Language > Interfaces and Inheritance

Writing Final Classes and Methods

You can declare some or all of a class's methods final. You use the final keyword in a method declaration to indicate that the method cannot be overridden by subclasses. The Object class does this—a number of its methods are final.

You might wish to make a method final if it has an implementation that should not be changed and it is critical to the consistent state of the object. For example, you might want to make the getFirstPlayer method in this ChessAlgorithm class final:

class ChessAlgorithm {
    enum ChessPlayer { WHITE, BLACK }
    ...
    final ChessPlayer getFirstPlayer() {
        return ChessPlayer.WHITE;
    }
    ...
}
Methods called from constructors should generally be declared final. If a constructor calls a non-final method, a subclass may redefine that method with surprising or undesirable results.

Note that you can also declare an entire class final — this prevents the class from being subclassed. This is particularly useful, for example, when creating an immutable class like the String class.


Problems with the examples? Try Compiling and Running the Examples: FAQs.
Complaints? Compliments? Suggestions? Give us your feedback.

Previous page: Object as a Superclass
Next page: Abstract Methods and Classes