大话设计模式-中介者模式

需求
实现一个模拟中介介绍两个人认识的程序。
实现

public abstract class Mediator
{
	abstract public void Send(String message,Colleague colleague);
}

public class Colleague 
{
	protected Mediator mediator;
	public Colleague(Mediator mediator)
	{
		this.mediator=mediator;
	}
}

public class ConcreteMediator extends Mediator
{
	private ConcreteColleague1 colleague1;
	private ConcreteColleague2 colleague2;
	public ConcreteColleague1 getColleague1() 
	{
		return colleague1;	
	}
	public void setColleague1(ConcreteColleague1 colleague1) 
	{
		this.colleague1=colleague1;
	}
	public ConcreteColleague2 getColleague2()
	{
		return colleague2;
	}
	public void setColleague2(ConcreteColleague2 colleague2)
	{
		this.colleague2=colleague2;
	}
	public void Send(String message,Colleague colleague)
	{
		if(colleague==colleague1) colleague2.Notify(message);
		if(colleague==colleague2) colleague1.Notify(message);
	}
}

public class ConcreteColleague1 extends Colleague
{
	public ConcreteColleague1(Mediator mediator)
	{
		super(mediator);
	}
	public void Send(String message)
	{
		mediator.Send(message,this);
	}
	public void Notify(String message)
	{
		System.out.println("colleague1 get message:"+message);
	}
}

public class ConcreteColleague2 extends Colleague
{
	public ConcreteColleague2(Mediator mediator)
	{
		super(mediator);
	}
	public void Send(String message)
	{
		mediator.Send(message,this);
	}
	public void Notify(String message)
	{
		System.out.println("colleague2 get message:"+message);
	}
}

public class Main
{  	  
    public static void main(String[] args)
    {  
       ConcreteMediator m=new  ConcreteMediator();
       ConcreteColleague1 c1=new ConcreteColleague1(m);
       ConcreteColleague2 c2=new ConcreteColleague2(m);
       m.setColleague1(c1);
       m.setColleague2(c2);
       c1.Send("Hello!");
       c2.Send("Hello,too!");
    }  
}  

中介者模式，定义一个中介对象来封装系列对象之间的交互。中介者使各个对象不需要显示地相互引用，从而使其耦合性松散，而且可以独立地改变他们之间的交互。一组定义良好的对象，现在要进行复杂的通信时或者定制一个分布在多个类中的行为，而又不想生成太多的子类时可以考虑使用中介者模式。可以看出，中介对象主要是用来封装行为的，行为的参与者就是那些对象，但是通过中介者，这些对象不用相互知道。使用中介者模式降低了系统对象之间的耦合性，使得对象易于独立的被复用；提高系统的灵活性，使得系统易于扩展和维护。同时，中介者模式的缺点也是显而易见的，因为这个中介承担了较多的责任，所以一旦出现问题，整个系统就会受到重大的影响。