Declare classes final in Java to prevent inheritance, and ensure the immutability of objects (like String). When a class should never change state after creation. …see more ...

Marking a class as final prevents all inheritance, by anyone -- even the original developer cannot inherit from one of their own final classes. It's a powerful but potentially messy design constraint.

An abstract class is a class that is declared abstract using the abstract keyword. It may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed.

Example: public final class Circle { private final double radius; ... Declare classes final in Java to prevent inheritance, and ensure the immutability of objects (like String).