裝飾模式：動態地給一個物件新增一些額外的職責，就增加功能來說，裝飾模式比生成子類更加靈活。

Component是定義了一個物件介面，可以給這些物件動態地新增職責，ConcreteComponent是定義了一個具體的物件，也可以給這些物件新增一些職責。Decorator，裝飾抽象類，繼承了Component，從外類來擴充套件Component類的功能，但對於Component來說，是無需知道Decorator的存在的，至於ConcreteDecorator就是具體的裝飾物件，起到給Component新增職責的功能。

public abstract class Component {

    public abstract void Operation();
}
 

public class ConcreteComponent extends Component {

    @Override
    public void Operation() {

    }
}

public abstract class Decorator extends Component {

    protected Component component;

    public void setComponent(Component component) {
        this.component = component;
    }

    @Override
    public void Operation() {
        if (component != null) {
            component.Operation();
        }
    }
}
 

public class ConcreteDecoratorA extends Decorator {

    private String addedState;

    @Override
    public void Operation() {
        super.Operation();
        addedState = "New State";
        System.out.println("對具體物件A的操作");
    }
}

public class ConcreteDecoratorB extends Decorator {

    @Override
    public void Operation() {
        super.Operation();
        AddedBehavior();
        System.out.println("具體裝飾物件B的操作");
    }

    private void AddedBehavior() {

    }
}
 

public class Main {

    public static void main(String[] args) {
        ConcreteComponent c = new ConcreteComponent();
        ConcreteDecoratorA decoratorA = new ConcreteDecoratorA();
        ConcreteDecoratorB decoratorB = new ConcreteDecoratorB();

        decoratorA.setComponent(c);
        decoratorB.setComponent(decoratorA);
        decoratorB.Operation();

    }
}