Question

I have a simple scenario. I’d like to create a new instance of the class below.

class A implements Fancy {
    void my() {
        Fancy b = // new X(); where X could be A or B
    }
}

When you have a B which implements Fancy as well.

Answer 1

Create an abstract class AbstractFancy with a create method:

abstract class AbstractFancy implements Fancy {
    abstract Fancy create();

    void my() {
        Fancy b = create();
        //....
    }
}

In each class implement the create method:

class A extends AbstractFancy {
    Fancy create() {
        return new A();
    }
}
class B extends AbstractFancy {
    Fancy create() {
        return new B();
    }
}