Controlling subclassing of classes

The final keyword has one additional usage. We can use final as a modifier before the class keyword in the class declaration to indicate Java that we want to generate a final class, that is, a class that cannot be extended or subclassed. Java 9 won't allow us to create a subclass for a final class.

Now, we will create the VirtualDomesticCat abstract class and then we will declare a concrete subclass named MaineCoon as a final class. This way, we will make sure that nobody will be able to create a subclass of MaineCoon. The following lines show the code for the VirtualDomesticCat abstract class. The code file for the sample is included in the java_9_oop_chapter_07_01 folder, in the example07_02.java file.

public abstract class VirtualDomesticCat extends VirtualDomesticMammal {
    public VirtualDomesticCat(
        int age, 
        boolean isPregnant, 
        String name, 
        String favoriteToy) {
        super(age, isPregnant, name, favoriteToy);...