New to Java

Hello everybody. I have a question. Suppose I have a Class hierarchy like :

public class ClassA extends Class {
	public ClassA() {
	}

	public class ClassB extends ClassA {
		public ClassB() {
		}
	}
}

And I want to Instantiate ClassB like

 new ClassA().ClassB();

. Is it possible or valid? If possible then which modifier should I use or any other way.
Thank you.