抽象类实例化内部类

Question

I have an abstract class with a non-static non abstract inner class that I have to instantiate from a static method. how can this be done?

This is basically what I am trying to do:

abstract class Program
{
    private static Window window;

    public static void main(String[] args)
    {
        Program program = new Program();
        window = program.new Window();
    }

    abstract void Update();

    class Window
    {
        public Window()
        {
            //some code
        }

        public void someMethod()
        {
            Update();
        }
    }
}

I know you cannot instantiate an abstract class, and you can't instantiate the inner class from a static method without an instance of the outer class, so I have no idea what to do.

Answer 1

What you can do is just create one class which extends your abstract class and in that class you can instantiate your inner class like following:

public class TestProgram extends Program
 {

  public static void main(String[] args)
   {
    Program program = new TestProgram();
    Window window = program.new Window();
  }
}

Answer 2

The simplest answer seems to be create an implementation of Program that you can use to instantiate Window objects from.

More generally, I think your paradox is your answer. You're trying to design something that won't work within the language constraints and you'll have to give up the abstract nature of Program or make Window a class you can create outside of a Program.

Answer 3

Why do you have your main method inside of an abstract class ?

The bigger problem here is the design. What is the point of having that Window class an inner class? If you want to instantiate that object from within the abstract class, just make Window it's own top level class.

It doesnt appear to access anything from its containing class, so why have it be an inner class?