Static Class in Abstract Class

Question

abstract class MyClass{

    static class StaticClass{
        public void showAdd(){
            System.out.println(" show add");
        }
    }
}

public class SampleClass extends MyClass{

    public static void main(String[] args){
         MyClass myClass = new SampleClass();
         MyClass.StaticClass staticClass = new MyClass.StaticClass();
         staticClass.showAdd();
    }
}

Output is proper as expected but how can we write new with an abstract class??

Answer 1

You are not doing new on the abstract class but on the inner class that exists in this abstract class. In this case the abstract class is acting as a namespace.

Answer 2

You cannot instantiate an abstract class. Your example "works" because you are not really instantiating an abstract class.

MyClass myClass = new SampleClass();

SampleClass is a child and an implementation of the MyClass class, and because of that it is not abstract. So that line simply works as it should. Try replace new SampleClass() to new MyClass() and you will get an compiler error.

MyClass.StaticClass staticClass = new MyClass.StaticClass();

which is the same in this case as:

StaticClass staticClass = new StaticClass();

Is just an instantiation of a Inner Class declared inside an abstract class. Since this inner class is not abstract it may be instantiated.