Java 프레임워크에서는 디자인 패턴이 어떻게 구현됩니까?

// 主题接口
interface LogSubject {
    void attach(LogObserver observer);
    void detach(LogObserver observer);
    void notifyObservers(LogEntry logEntry);
}

// 具体主题（日志记录器）
class LoggerSubject implements LogSubject {
    private List<LogObserver> observers = new ArrayList<>();

    @Override
    public void attach(LogObserver observer) {
        observers.add(observer);
    }

    @Override
    public void detach(LogObserver observer) {
        observers.remove(observer);
    }

    @Override
    public void notifyObservers(LogEntry logEntry) {
        for (LogObserver observer : observers) {
            observer.update(logEntry);
        }
    }

    public void log(String message) {
        LogEntry logEntry = new LogEntry(message);
        notifyObservers(logEntry);
    }
}

// 观察者接口
interface LogObserver {
    void update(LogEntry logEntry);
}

// 具体观察者（控制台日志记录器）
class ConsoleLoggerObserver implements LogObserver {
    @Override
    public void update(LogEntry logEntry) {
        System.out.println(logEntry.getMessage());
    }
}

// 使用该模式
LoggerSubject loggerSubject = new LoggerSubject();
ConsoleLoggerObserver consoleLoggerObserver = new ConsoleLoggerObserver();
loggerSubject.attach(consoleLoggerObserver);

loggerSubject.log("Hello World!"); // 将消息打印到控制台