中介者模式（Mediator），用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显示的相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。

public abstract class Member {
    protected Mediator mediator;
    public Mediator getMediator() {
        return mediator;
    }

    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }

    public abstract void notifyOthers(String info);
    public void getInfo(String fromWho, String info){
        System.out.println(this.getClass().getName() + " 收到来自 " + fromWho + " 的消息: " + info);
    }
}

public class Member01 extends Member{
    public void notifyOthers(String info){
        super.mediator.notifyOthers(info,this);
    }
}

public class Member02 extends Member{
    public void notifyOthers(String info){
        super.mediator.notifyOthers(info,this);
    }
}

public class Member03 extends Member{
    public void notifyOthers(String info){
        super.mediator.notifyOthers(info,this);
    }
}

public class Mediator {
    private Member member01;
    private Member member02;
    private Member member03;

    public Mediator(Member member01, Member member02, Member member03) {
        this.member01 = member01;
        this.member02 = member02;
        this.member03 = member03;
    }

    public void notifyOthers(String info, Member member){
        String name = member.getClass().getName();
        name = name.substring(name.lastIndexOf(".")+1);
        switch (name){
            case "Member01": {
                member02.getInfo(name,info);
                member03.getInfo(name,info);
                break;
            }
            case "Member02": {
                member01.getInfo(name,info);
                member03.getInfo(name,info);
                break;
            }
            case "Member03": {
                member01.getInfo(name,info);
                member02.getInfo(name,info);
                break;
            }
        }
    }
}

public class Client {
    public static void main(String[] args) {

        Member member01 = new Member01();
        Member member02 = new Member02();
        Member member03 = new Member03();
        Mediator mediator = new Mediator(member01, member02, member03);
        member01.setMediator(mediator);
        member02.setMediator(mediator);
        member03.setMediator(mediator);

        member01.notifyOthers("消息1");
        member02.notifyOthers("消息2");
        member03.notifyOthers("消息3");
    }
}

designPatterns.behaviorTypePatterns.mediatorPattern.member.Member02 收到来自 Member01 的消息: 消息1
designPatterns.behaviorTypePatterns.mediatorPattern.member.Member03 收到来自 Member01 的消息: 消息1
designPatterns.behaviorTypePatterns.mediatorPattern.member.Member01 收到来自 Member02 的消息: 消息2
designPatterns.behaviorTypePatterns.mediatorPattern.member.Member03 收到来自 Member02 的消息: 消息2
designPatterns.behaviorTypePatterns.mediatorPattern.member.Member01 收到来自 Member03 的消息: 消息3
designPatterns.behaviorTypePatterns.mediatorPattern.member.Member02 收到来自 Member03 的消息: 消息3

中介者模式很容易在系统中应用，也很容易在系统中误用。当系统出现了‘多对多’交互复杂的对象群时，不要急于使用中介者模式，而要先反思你的系统在设计上是不是合理。
…
Mediator的出现减少了各个Member的耦合，使得可以独立地改变和服用各个Mediator和Member。
…
由于把对象如何协作进行了抽象，将中介作为一个独立的概念并将其封装在一个对象中，这样关注的对象就从对象各自本身的行为转移到他们之间的交互上来，也就是站在一个更宏观的角度去看待系统。
…
由于Mediator控制了集中化，于是就把交互复杂性变为了中介者的复杂性，这就使得中介者会变得比任何一个Member都复杂。
————摘自《大话设计模式》