【设计模式-中介者模式】

定义

中介者模式（Mediator Pattern）是一种行为设计模式，通过引入一个中介者对象，来降低多个对象之间的直接交互，从而减少它们之间的耦合度。中介者充当不同对象之间的协调者，使得对象之间的通信变得简单且集中。

UML图

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Mediator（中介者接口）：定义中介者与同事之间的交互方法。
ConcreteMediator（具体中介者）：实现中介者接口，维护对同事对象的引用，并协调它们之间的交互。
Colleague（同事抽象类）：通常持有对中介者的引用，通过中介者进行通信。
ConcreteColleague（同事类）：具体的组件类，通常持有对中介者的引用，通过中介者进行通信。

代码

// Mediator interface
interface Mediator {void send(String message, Colleague colleague);
}// Concrete Mediator
class ChatMediator implements Mediator {private List<Colleague> colleagues = new ArrayList<>();public void addColleague(Colleague colleague) {colleagues.add(colleague);}@Overridepublic void send(String message, Colleague colleague) {for (Colleague c : colleagues) {// Prevent sending message back to the senderif (c != colleague) {c.receive(message);}}}
}// Colleague interface
abstract class Colleague {protected Mediator mediator;public Colleague(Mediator mediator) {this.mediator = mediator;}public abstract void send(String message);public abstract void receive(String message);
}// Concrete Colleague
class User extends Colleague {private String name;public User(Mediator mediator, String name) {super(mediator);this.name = name;}@Overridepublic void send(String message) {System.out.println(name + ": Sending message: " + message);mediator.send(message, this);}@Overridepublic void receive(String message) {System.out.println(name + ": Received message: " + message);}
}// Client code
public class MediatorPatternDemo {public static void main(String[] args) {ChatMediator mediator = new ChatMediator();User user1 = new User(mediator, "Alice");User user2 = new User(mediator, "Bob");mediator.addColleague(user1);mediator.addColleague(user2);user1.send("Hello Bob!");user2.send("Hi Alice!");}
}