Lock

Posted 2021-03-08 shun-w

JVM提供了synchronized关键字来实现对变量的同步访问以及用wait和notify来实现线程间通信。在jdk1.5以后，JAVA提供了Lock类来实现和synchronized一样的功能，并且还提供了Condition来显示线程间通信。
c1打印完通知c2,c2打印完通知c3

class Hello {
    private int number = 1;//A:1, B:2, C:3
    private Lock lock = new ReentrantLock();
    private Condition c1 = lock.newCondition();
    private Condition c2 = lock.newCondition();
    private Condition c3 = lock.newCondition();

    //判断
    public void print5() {
        lock.lock();
        try {
            while (number != 1) {
                c1.await();
            }
            for (int i = 0; i < 5; i++) {
                System.out.println(Thread.currentThread().getName() + "	" + number);
            }

            number=2;
            c2.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void print10() {
        lock.lock();
        try {
            while (number != 2) {
                c2.await();
            }
            for (int i = 0; i < 10; i++) {
                System.out.println(Thread.currentThread().getName() + "	" + number);
            }

            number=3;
            c3.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void print8() {
        lock.lock();
        try {
            while (number != 3) {
                c3.await();
            }
            for (int i = 0; i < 8; i++) {
                System.out.println(Thread.currentThread().getName() + "	" + number);
            }

            number=1;
            c1.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

}