interface MyInterface {
    void writeHelloWorld();
}
class A implements MyInterface {
    @Override
    public void writeHelloWorld() {
        System.out.println("A " + "says: Hello World");
    }
}
class B implements MyInterface {
    @Override
    public void writeHelloWorld() {
        System.out.println("B " + "says: Hello World");
    }
}
class MyClass {
    public static void main(String[] args) {
        MyInterface myInterfaceA = new A();
        MyInterface myInterfaceB = new B();
        myInterfaceA.writeHelloWorld();
        myInterfaceB.writeHelloWorld();
    }
}