10.25

中介者模式

下面是一個簡單的示例，展示瞭如何在 Java 中實現中介者模式：

// 中介者介面
interface Mediator {
    void sendMessage(String message, Colleague colleague);
}

// 抽象同事類
abstract class Colleague {
    protected Mediator mediator;

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

    public abstract void receiveMessage(String message);
    public abstract void sendMessage(String message);
}

// 具體同事類A
class ConcreteColleagueA extends Colleague {
    public ConcreteColleagueA(Mediator mediator) {
        super(mediator);
    }

    public void receiveMessage(String message) {
        System.out.println("Colleague A received message: " + message);
    }

    public void sendMessage(String message) {
        mediator.sendMessage(message, this);
    }
}

// 具體同事類B
class ConcreteColleagueB extends Colleague {
    public ConcreteColleagueB(Mediator mediator) {
        super(mediator);
    }

    public void receiveMessage(String message) {
        System.out.println("Colleague B received message: " + message);
    }

    public void sendMessage(String message) {
        mediator.sendMessage(message, this);
    }
}

// 具體中介者類
class ConcreteMediator implements Mediator {
    private Colleague colleagueA;
    private Colleague colleagueB;

    public void setColleagueA(Colleague colleagueA) {
        this.colleagueA = colleagueA;
    }

    public void setColleagueB(Colleague colleagueB) {
        this.colleagueB = colleagueB;
    }

    public void sendMessage(String message, Colleague colleague) {
        if (colleague == colleagueA) {
            colleagueB.receiveMessage(message);
        } else if (colleague == colleagueB) {
            colleagueA.receiveMessage(message);
        }
    }
}

// 客戶端程式碼
public class MediatorPatternExample {
    public static void main(String[] args) {
        ConcreteMediator mediator = new ConcreteMediator();

        ConcreteColleagueA colleagueA = new ConcreteColleagueA(mediator);
        ConcreteColleagueB colleagueB = new ConcreteColleagueB(mediator);

        mediator.setColleagueA(colleagueA);
        mediator.setColleagueB(colleagueB);

        colleagueA.sendMessage("Hello from Colleague A!");
        colleagueB.sendMessage("Hi from Colleague B!");
    }
}