How can I create a new instance of a subclass from a static method in its superclass in Java?

Question

I have an abstract singleton class and I want it to have an instance field that represents the singleton's instance. I tried doing this:

public abstract class AbstractClass {
    private static AbstractClass instance;

    public static AbstractClass getInstance() {
        return instance == null ? this.getClass().newInstance() : instance;
    }    
}

I want this to function so that when I call it from a subclass of AbstractClass it returns an instance of that subclass, not an instance of AbstractClass , which is why I tried using this#getClass() instead of just AbstractClass . This of course gives me an error stating "Cannot use this in a static context". Is there a way I can generate a new instance of a subclass in a static method in its superclass?

Answer 1

this can not be used inside a static method because there is no explicit object to resolve for the this reference.

In addition to this constraint, Parent class does not know about the possible subclasses(unless sealed ) that can extend from it.

So, it can't create an explicit instance of a subclass.

Based on your problem, you may want to approach some form of Factory pattern to manage object creation. (or other creational pattern)