interface Component {
  public void operation();
}
ConcreteComponent : 实现 Component 定义的接口。
class ConcreteComponent implements Component {
  @Override
  public void operation() {
    System.out.println("初始行为");
  }
}

class Decorator implements Component {
  // 持有一个 Component 对象，和 Component 形成聚合关系
  protected Component component;
  
  // 传入要进一步修饰的对象
  public Decorator(Component component) {
    this.component = component;
  }
  
  @Override
  // 调用要修饰对象的原方法
  public void operation() {
    component.operation();
  }
}

class ConcreteDecoratorA extends Decorator {
  private String addedState = "新属性1";
  
  public ConcreteDecoratorA(Component component) {
    super(component);
  }
  
  public void operation() {
    super.operation();
    System.out.println("添加属性: " + addedState);
  }
}

class ConcreteDecoratorB extends Decorator {
  public ConcreteDecoratorB(Component component) {
    super(component);
  }

  public void operation() {
    super.operation();
    AddedBehavior();
  }
  
  public void AddedBehavior() {
    System.out.println("添加行为");
  }
}

public class DecoratorPattern {
  public static void main(String[] args) {
    Component component = new ConcreteComponent();
    component.operation();
    
    System.out.println("======================================");
    Decorator decoratorA = new ConcreteDecoratorA(component);
    decoratorA.operation();
    
    System.out.println("======================================");
    Decorator decoratorB = new ConcreteDecoratorB(decoratorA);
    decoratorB.operation();
  }
}

初始行为
======================================
初始行为
添加属性: 新属性1
======================================
初始行为
添加属性: 新属性1
添加行为