中介者模式

中介者模式是一种行为型设计模式，它包含了一个中介对象，该对象通常用于简化一组对象与对象之间的通信。中介者使得各个同事对象不需要显式地相互引用，从而使其在处理一组对象之间的交互时更加灵活和易于维护。

以下是一个简单的Java中介者模式的实现示例：

// 同事类的基本接口
interface Colleague {
    void sendMessage(String message);
}
 
// 具体的同事类
class ConcreteColleagueA implements Colleague {
    private Mediator mediator;
    
    public ConcreteColleagueA(Mediator mediator) {
        this.mediator = mediator;
        mediator.register(this);
    }
    
    @Override
    public void sendMessage(String message) {
        System.out.println("同事A发送信息：" + message);
    }
}
 
class ConcreteColleagueB implements Colleague {
    private Mediator mediator;
    
    public ConcreteColleagueB(Mediator mediator) {
        this.mediator = mediator;
        mediator.register(this);
    }
    
    @Override
    public void sendMessage(String message) {
        System.out.println("同事B发送信息：" + message);
    }
}
 
// 中介者接口
interface Mediator {
    void register(Colleague colleague);
    void send(String message, Colleague colleague);
}
 
// 中介者类
class ConcreteMediator implements Mediator {
    private ConcreteColleagueA colleagueA;
    private ConcreteColleagueB colleagueB;
    
    @Override
    public void register(Colleague colleague) {
        if (colleague instanceof ConcreteColleagueA) {
            colleagueA = (ConcreteColleagueA) colleague;
        } else if (colleague instanceof ConcreteColleagueB) {
            colleagueB = (ConcreteColleagueB) colleague;
        }
    }
 
    @Override
    public void send(String message, Colleague colleague) {
        if (colleague == colleagueA) {
            colleagueB.sendMessage(message);
        } else {
            colleagueA.sendMessage(message);
        }
    }
}
 
// 客户端代码
public class Client {
    public static void main(String[] args) {
        Mediator mediator = new ConcreteMediator();
        Colleague colleagueA = new ConcreteColleagueA(mediator);
        Colleague colleagueB = new ConcreteColleagueB(mediator);
        
        colleagueA.sendMessage("你好，同事B");
        colleagueB.sendMessage("你好，同事A");
    }
}

在这个示例中，我们定义了一个Mediator接口和一个ConcreteMediator中介者类。同时，我们定义了两个同事类ConcreteColleagueA和ConcreteColleagueB，它们都实现了Colleague接口。在main方法中，我们创建了一个中介者对象和两个同事对象，并展示了它们如何通过中介者进行通信。这个简单的例子展示了中介者模式的基本原理和结构。