ReentranReadWriteLock 使用案例

 ReentranReadWriteLock使用案例

/**
 * ReentranReadWriteLock 使用案例
 * 读线程共享
 * 写线程互斥
 */
public class ReentrantReadWriteLockExample {
    private String news;
    private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
 
    public String readNews() {
        lock.readLock().lock();
        try {
            // 读线程睡眠1秒, 观察打印时间
            Thread.sleep(1000);
            System.out.println(Thread.currentThread().getName() + " " + LocalDateTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss")) + " is reading the news: " + news);
            return news;
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            lock.readLock().unlock();
        }
    }
 
    public void writeNews(String updatedNews) {
        lock.writeLock().lock();
        try {
            // 让写线程睡眠两秒,这样可以观察到写线程阻塞
            Thread.sleep(2000); 
            System.out.println(Thread.currentThread().getName() + " " +  LocalDateTime.now().format(DateTimeFormatter.ofPattern("hh:mm:ss"))  + " is updating the news to: " + updatedNews);
            news = updatedNews;
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            lock.writeLock().unlock();
        }
    }
 
    public static void main(String[] args) {
        ReentrantReadWriteLockExample newsData = new ReentrantReadWriteLockExample();
 
        // 创建多个读线程
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                newsData.readNews();
            }).start();
        }
 
        // 创建多个写线程
        for (int i = 0; i < 5; i++) {
            new Thread(()->{
                newsData.writeNews("Breaking news: JavaAssistant is awesome!");
            }).start();
        }
    }
}

 输出结果

从结果可以看出，读线程是同时读取了news，而写线程则是一个个的读。

Thread-0 10:11:45 is reading the news: null
Thread-7 10:11:45 is reading the news: null
Thread-6 10:11:45 is reading the news: null
Thread-1 10:11:45 is reading the news: null
Thread-5 10:11:45 is reading the news: null
Thread-3 10:11:45 is reading the news: null
Thread-2 10:11:45 is reading the news: null
Thread-9 10:11:45 is reading the news: null
Thread-4 10:11:45 is reading the news: null
Thread-8 10:11:45 is reading the news: null
Thread-10 10:11:47 is updating the news to: Breaking news: JavaAssistant is awesome!
Thread-11 10:11:49 is updating the news to: Breaking news: JavaAssistant is awesome!
Thread-12 10:11:51 is updating the news to: Breaking news: JavaAssistant is awesome!
Thread-13 10:11:53 is updating the news to: Breaking news: JavaAssistant is awesome!
Thread-14 10:11:55 is updating the news to: Breaking news: JavaAssistant is awesome!