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notes/设计模式 - 中介者.md

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+## 5. 中介者（Mediator）
+
+### Intent
+
+集中相关对象之间复杂的沟通和控制方式。
+
+### Class Diagram
+
+
+
+- Mediator：中介者，定义一个接口用于与各同事（Colleague）对象通信。
+- Colleague：同事，相关对象
+
+<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/30d6e95c-2e3c-4d32-bf4f-68128a70bc05.png"/> </div><br>
+
+### Implementation
+
+Alarm（闹钟）、CoffeePot（咖啡壶）、Calendar（日历）、Sprinkler（喷头）是一组相关的对象，在某个对象的事件产生时需要去操作其它对象，形成了下面这种依赖结构：
+
+<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/82cfda3b-b53b-4c89-9fdb-26dd2db0cd02.jpg"/> </div><br>
+
+使用中介者模式可以将复杂的依赖结构变成星形结构：
+
+<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/5359cbf5-5a79-4874-9b17-f23c53c2cb80.jpg"/> </div><br>
+
+```java
+public abstract class Colleague {
+    public abstract void onEvent(Mediator mediator);
+}
+```
+
+```java
+public class Alarm extends Colleague {
+
+    @Override
+    public void onEvent(Mediator mediator) {
+        mediator.doEvent("alarm");
+    }
+
+    public void doAlarm() {
+        System.out.println("doAlarm()");
+    }
+}
+```
+
+```java
+public class CoffeePot extends Colleague {
+    @Override
+    public void onEvent(Mediator mediator) {
+        mediator.doEvent("coffeePot");
+    }
+
+    public void doCoffeePot() {
+        System.out.println("doCoffeePot()");
+    }
+}
+```
+
+```java
+public class Calender extends Colleague {
+    @Override
+    public void onEvent(Mediator mediator) {
+        mediator.doEvent("calender");
+    }
+
+    public void doCalender() {
+        System.out.println("doCalender()");
+    }
+}
+```
+
+```java
+public class Sprinkler extends Colleague {
+    @Override
+    public void onEvent(Mediator mediator) {
+        mediator.doEvent("sprinkler");
+    }
+
+    public void doSprinkler() {
+        System.out.println("doSprinkler()");
+    }
+}
+```
+
+```java
+public abstract class Mediator {
+    public abstract void doEvent(String eventType);
+}
+```
+
+```java
+public class ConcreteMediator extends Mediator {
+    private Alarm alarm;
+    private CoffeePot coffeePot;
+    private Calender calender;
+    private Sprinkler sprinkler;
+
+    public ConcreteMediator(Alarm alarm, CoffeePot coffeePot, Calender calender, Sprinkler sprinkler) {
+        this.alarm = alarm;
+        this.coffeePot = coffeePot;
+        this.calender = calender;
+        this.sprinkler = sprinkler;
+    }
+
+    @Override
+    public void doEvent(String eventType) {
+        switch (eventType) {
+            case "alarm":
+                doAlarmEvent();
+                break;
+            case "coffeePot":
+                doCoffeePotEvent();
+                break;
+            case "calender":
+                doCalenderEvent();
+                break;
+            default:
+                doSprinklerEvent();
+        }
+    }
+
+    public void doAlarmEvent() {
+        alarm.doAlarm();
+        coffeePot.doCoffeePot();
+        calender.doCalender();
+        sprinkler.doSprinkler();
+    }
+
+    public void doCoffeePotEvent() {
+        // ...
+    }
+
+    public void doCalenderEvent() {
+        // ...
+    }
+
+    public void doSprinklerEvent() {
+        // ...
+    }
+}
+```
+
+```java
+public class Client {
+    public static void main(String[] args) {
+        Alarm alarm = new Alarm();
+        CoffeePot coffeePot = new CoffeePot();
+        Calender calender = new Calender();
+        Sprinkler sprinkler = new Sprinkler();
+        Mediator mediator = new ConcreteMediator(alarm, coffeePot, calender, sprinkler);
+        // 闹钟事件到达，调用中介者就可以操作相关对象
+        alarm.onEvent(mediator);
+    }
+}
+```
+
+```java
+doAlarm()
+doCoffeePot()
+doCalender()
+doSprinkler()
+```
+
+### JDK
+
+- All scheduleXXX() methods of [java.util.Timer](http://docs.oracle.com/javase/8/docs/api/java/util/Timer.html)
+- [java.util.concurrent.Executor#execute()](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Executor.html#execute-java.lang.Runnable-)
+- submit() and invokeXXX() methods of [java.util.concurrent.ExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html)
+- scheduleXXX() methods of [java.util.concurrent.ScheduledExecutorService](http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ScheduledExecutorService.html)
+- [java.lang.reflect.Method#invoke()](http://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Method.html#invoke-java.lang.Object-java.lang.Object...-)
+
+
+
+
+
+
+<div align="center"><img width="320px" src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/githubio/公众号二维码-2.png"></img></div>