Java 演示ReadWriteLock使用的示例

我试图理解

ReadWriteLock

的概念，并实现了下面的简单示例。据我所知，每当一个线程具有

readlock

，另一个线程就可以获得

readlock

。但是对于具有

writelock

的线程，只有在另一个线程释放锁之前，其他线程才能获取

写/读锁。然而，从下面程序的输出中，我注意到在
WriterOdd
释放锁（打印释放锁的输出）之前，
Reader
线程进入并读取
number
字符串。是因为刚刚释放
写锁
之后，
读卡器
线程进来，然后打印了释放
写锁
的打印语句吗

public static void main(String[] args) {

    new Thread(new Reader(), "Reader 1").start();
    new Thread(new Reader(), "Reader 2").start();
    new Thread(new WriterEven(), "Writer Even").start();
    new Thread(new WriterOdd(), "Writer Odd").start();

}

public static class Reader implements Runnable {

    public void run() {

        for (int i = 1; i <= 6; i++) {
            rwl.readLock().lock();
            // rl.lock();
            System.out.println(Thread.currentThread().getName() + "  is reading" + number);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                rwl.readLock().unlock();
            }
        }

    }

}

public static class WriterEven implements Runnable {

    public void run() {
        System.out.println(Thread.currentThread().getName() + " is trying  writing");
        rwl.writeLock().lock();
        System.out.println(Thread.currentThread().getName() + " got the lock");
        for (int i = 2; i <= 6; i += 2) {

            System.out.println(Thread.currentThread().getName() + " is writing");
            number = number.concat(" " + i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {

            }

        }
        rwl.writeLock().unlock();

        System.out.println(Thread.currentThread().getName() + " left the lock");

    }

}

public static class WriterOdd implements Runnable {

    public void run() {
        System.out.println(Thread.currentThread().getName() + " is trying  writing");
        rwl.writeLock().lock();
        System.out.println(Thread.currentThread().getName() + " got the lock");
        for (int i = 1; i <= 5; i += 2) {

            System.out.println(Thread.currentThread().getName() + " is writing");
            number = number.concat(" " + i);
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {

            }

        }
        rwl.writeLock().unlock();
        System.out.println(Thread.currentThread().getName() + " left the lock");

    }

}

在释放锁之后，写入有关释放写锁的控制台消息的代码行

rwl.writeLock().unlock();
// here readers can read already
// because they are free to aquire lock
System.out.println(Thread.currentThread().getName() + " left the lock");

旁白：在最后一个街区解锁。
rwl.writeLock().unlock();
// here readers can read already
// because they are free to aquire lock
System.out.println(Thread.currentThread().getName() + " left the lock");