小谈设计模式（6）—依赖倒转原则

// 定义抽象接口
public interface MessageSender {
    void sendMessage(String message);
}

// 具体实现类1
public class EmailSender implements MessageSender {
    @Override
    public void sendMessage(String message) {
        System.out.println("Sending email: " + message);
    }
}

// 具体实现类2
public class SmsSender implements MessageSender {
    @Override
    public void sendMessage(String message) {
        System.out.println("Sending SMS: " + message);
    }
}

// 高层模块，依赖于抽象接口
public class NotificationService {
    private MessageSender messageSender;

    // 通过构造函数进行依赖注入
    public NotificationService(MessageSender messageSender) {
        this.messageSender = messageSender;
    }

    public void sendNotification(String message) {
        // 调用抽象接口的方法
        messageSender.sendMessage(message);
    }
}

// 测试代码
public class Main {
    public static void main(String[] args) {
        // 创建具体实现类的对象
        MessageSender emailSender = new EmailSender();
        MessageSender smsSender = new SmsSender();

        // 创建高层模块的对象，并传入具体实现类的对象
        NotificationService emailNotificationService = new NotificationService(emailSender);
        NotificationService smsNotificationService = new NotificationService(smsSender);

        // 调用高层模块的方法
        emailNotificationService.sendNotification("Hello, this is an email notification.");
        smsNotificationService.sendNotification("Hello, this is an SMS notification.");
    }
}