public class Client {
  public static void main(String[] args) {
    ConcreteComponent c = new ConcreteComponent();
    ConcreteDecoratorA da = new ConcreteDecoratorA();
    ConcreteDecoratorB db = new ConcreteDecoratorB();

    da.setComponent(c);
    db.setComponent(da);

    db.operation();
  }
}