final class in java

Final Classes and Methods 

Inheritance is surely one of the highly useful features in Java. But at times, it may be desired that a class should not be extendable by other classes to prevent exploitation. For such purpose, we have the final keyword. We have already seen even what final variables are. Final classes and methods are also similar. A class declared as final cannot be extended while a method declared as final cannot be overridden in its subclasses. A method or a class is declared to be final using the final keyword. Though a final class cannot be extended, it can extend other classes. In simpler words, a final class can be a sub class but not a super class.

final public class A {
    //code
}

Resource: http://www.javawithus.com/tutorial/final-classes-and-methods