观察者模式：花与蜜蜂

发表于 Bearbeitet am 分类于

1、花与蜜蜂

一朵花有Open和Close两种状态，3只蜂鸟在花Open的时候去采蜜，在花Close的时候要回巢，用面向对象技术和Design Pattern方法模拟上面过程，输出如下：

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Flow Open
Hummingbird 1’s breakfast time!
Hummingbird 2’s breakfast time!
Hummingbird 3’s breakfast time!
Flow Close
Hummingbird 1’s bed time!
Hummingbird 2’s bed time!
Hummingbird 3’s bed time!

要求：

  • 1）使用一种Design Pattern方法，使花和蜜蜂之间松耦合，用你最熟悉的计算机语言写出上面完整程序；
  • 2）画出UML类图。

2、分析

  • 1、花只有一朵，但有不同状态
  • 2、蜜蜂有N只，且根据花的状态不同来通知蜜蜂实现不同的行为

    所以可以判断为明显的一对多的观察者模式

3、实现

  • 1）被观察者 - 花

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    import java.util.Observable;

    public class Flower extends Observable {
        public static final String Flow_Open = "Flow Open";
        public static final String Flow_Close = "Flow Close";

        private String status;

        public String getStatus() {
            return status;
        }

        public void setStatus(String status) {
            super.setChanged();
            this.status = status;
            System.out.println(status);
            //通知所有观察者
            notifyObservers(status);
        }

    }

  • 2）观察者 - 蜜蜂

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    import java.util.Observable;
    import java.util.Observer;

    public class Hummingbird implements Observer {

        private String name;

        public Hummingbird(String name) {
            // TODO Auto-generated constructor stub
            this.name = name;
        }

        @Override
        public void update(Observable observable, Object data) {
            // TODO Auto-generated method stub
            String status = data.toString();
            if (Flower.Flow_Open.equals(status)) {
                System.out.println(name + " breakfast time!");
            } else {
                System.out.println(name + " bed time!");
            }
        }

    }

  • 3）测试

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    public class Test {
        public static void main(String[] args) {
            Flower flower = new Flower();
            
            Hummingbird hummingbird1 = new Hummingbird("Hummingbird 1’s");
            flower.addObserver(hummingbird1);
            
            Hummingbird hummingbird2 = new Hummingbird("Hummingbird 2’s");
            flower.addObserver(hummingbird2);
            
            Hummingbird hummingbird3 = new Hummingbird("Hummingbird 3’s");
            flower.addObserver(hummingbird3);

            flower.setStatus(Flower.Flow_Open);
            
            flower.setStatus(Flower.Flow_Close);
        }
    }