What are final classes in Java?

The final modifier for finalizing the implementations of classes, methods, and variables.

The main purpose of using a class being declared as final is to prevent the class from being subclassed. If a class is marked as final then no class can inherit any feature from the final class.

You cannot extend a final class. If you try it gives you a compile time error.

Example

final class Super {
   private int data = 30;
}
public class Sub extends Super{
   public static void main(String args[]){
   }
}

Output

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
   at newJavaExamples.Sub.main(Sub.java:9)