observal

Author: laileon

src/com/blankj/custom/desingn_pattern/observerable/Observer.java

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+package com.blankj.custom.desingn_pattern.observerable;
+
+/***
+ * 抽象观察者
+ * 定义了一个update()方法，当被观察者调用notifyObservers()方法时，观察者的update()方法会被回调。
+ * @author jstao
+ *
+ */
+public interface Observer {
+    void update(String message);
+}

src/com/blankj/custom/desingn_pattern/observerable/Observerable.java

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+package com.blankj.custom.desingn_pattern.observerable;
+
+/***
+ * 抽象被观察者接口
+ * 声明了添加、删除、通知观察者方法
+ * @author jstao
+ *
+ */
+public interface Observerable {
+
+    void registerObserver(Observer o);
+    void removeObserver(Observer o);
+    void notifyObserver();
+
+}

src/com/blankj/custom/desingn_pattern/observerable/Test.java

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+package com.blankj.custom.desingn_pattern.observerable;
+
+public class Test {
+
+    public static void main(String[] args) {
+        WechatServer server = new WechatServer();
+
+        Observer userZhang = new User("ZhangSan");
+        Observer userLi = new User("LiSi");
+        Observer userWang = new User("WangWu");
+
+        server.registerObserver(userZhang);
+        server.registerObserver(userLi);
+        server.registerObserver(userWang);
+        server.setInfomation("PHP是世界上最好用的语言！");
+
+        System.out.println("----------------------------------------------");
+        server.removeObserver(userZhang);
+        server.setInfomation("JAVA是世界上最好用的语言！");
+
+    }
+}

src/com/blankj/custom/desingn_pattern/observerable/User.java

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+package com.blankj.custom.desingn_pattern.observerable;
+
+public class User implements Observer {
+    private String name;
+    private String message;
+
+    public User(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public void update(String message) {
+        this.message = message;
+        read();
+    }
+
+    public void read() {
+        System.out.println(name + " 收到推送消息： " + message);
+    }
+}

src/com/blankj/custom/desingn_pattern/observerable/WechatServer.java

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+package com.blankj.custom.desingn_pattern.observerable;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 被观察者，也就是微信公众号服务
+ * 实现了Observerable接口，对Observerable接口的三个方法进行了具体实现
+ *
+ * @author jstao
+ */
+public class WechatServer implements Observerable {
+
+    //注意到这个List集合的泛型参数为Observer接口，设计原则：面向接口编程而不是面向实现编程
+    private List<Observer> list;
+    private String message;
+
+    public WechatServer() {
+        list = new ArrayList<Observer>();
+    }
+
+    @Override
+    public void registerObserver(Observer o) {
+        list.add(o);
+    }
+
+    @Override
+    public void removeObserver(Observer o) {
+        if (!list.isEmpty())
+            list.remove(o);
+    }
+
+    //遍历
+    @Override
+    public void notifyObserver() {
+        for (int i = 0; i < list.size(); i++) {
+            Observer oserver = list.get(i);
+            oserver.update(message);
+        }
+    }
+
+    public void setInfomation(String s) {
+        this.message = s;
+        System.out.println("微信服务更新消息： " + s);
+        //消息更新，通知所有观察者
+        notifyObserver();
+    }
+
+}