Java Reference
In-Depth Information
8.9 The final Keyword
Sometimes, we want to create a method and disallow it to be overridden. In our example,
we may want to fix the way the computeStrength method works. In other words, we want
to make sure that someone does not create a class called SpecialSuperhero where the
strength is calculated in a different way. Maybe this class will give unfair advantage to
special superheroes. In order to prevent this, we can define the computeStrength method
in the Superhero class as final . Here is the rewritten code.
public class Superhero extends FictionalCharacter
final double computeStrength() {
return goodPower respect Math . random ( ) ;
} ...
A final method cannot be overridden in a subclass. Polymorphism does not apply
to final methods.
Similar to methods, classes can also be defined as final .A final class cannot be
inherited from. For example, consider the following code.
public final class Superhero extends FictionalCharacter
This means that a SpecialSuperhero class that extends from the Superhero class
cannot be created.
8.10 Static Methods and Polymorphism
Note that polymorphism does not apply to static methods. In order to demonstrate
the consequences, we will add the memberCount static method to the FictionalCharacter
class. The method will simply return the number of fictional characters that are created.
public abstract class FictionalCharacter implements Comparable
private String name;
private static int memberCount = 0;
public FictionalCharacter () {
} public FictionalCharacter(String name) {
this .name = name;
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