hello.java

package com.company;

abstract class A {
    public abstract void hello();
}

abstract class B extends A {
}

class C extends B {
    public void hello() {
        System.out.println("hello world");
    }
}

interface IFactory {
    A factorize();
}

abstract class AbstractFactory implements IFactory {
    String dup(String s) {
        return s + s;
    }
}

class CFactory extends AbstractFactory {
    public A factorize() {
        return new C();
    }
}

class HelloFacade {
    public void hello() {
        IFactory f = new CFactory();
        A a = f.factorize();
        a.hello();
    }
}

public class Main {
    public static void main(String[] args) {
        HelloFacade f;
        f.hello();
    }
}