java wait()notify释放锁

来源：互联网发布：绘画人偶软件编辑：程序博客网时间：2024/06/05 22:44

调用obj.wait()会立即释放锁，，以便其他线程可以执行obj.notify()，但是notify()不会立刻立刻释放sycronized（obj）中的obj锁，必须要等notify()所在线程执行完synchronized（obj）块中的所有代码才会释放这把锁.
//而 yield(),sleep()不会释放锁。

见如下代码：

public class WaitNotify {static boolean flag = true;static Object lock = new Object();public static void main(String[] args) throws Exception {Thread waitThread = new Thread(new Wait(), "WaitThread");waitThread.start();TimeUnit.SECONDS.sleep(1);Thread notifyThread = new Thread(new Notify(), "NotifyThread");notifyThread.start();}static class Wait implements Runnable {public void run() {// 加锁，拥有lock的Monitorsynchronized (lock) {// 当条件不满足时，继续wait，同时释放了lock的锁while (flag) {try {System.out.println(Thread.currentThread()+ " flag is true. wait@ "+ new SimpleDateFormat("HH:mm:ss").format(new Date()));lock.wait();} catch (InterruptedException e) {}}// 条件满足时，完成工作System.out.println(Thread.currentThread()+ " flag is false. running@ "+ new SimpleDateFormat("HH:mm:ss").format(new Date()));}}}// wait()会立刻释放synchronized（obj）中的obj锁，以便其他线程可以执行obj.notify()// 但是notify()不会立刻立刻释放sycronized（obj）中的obj锁，必须要等notify()所在线程执行完synchronized（obj）块中的所有代码才会释放这把锁.// yield(),sleep()不会释放锁static class Notify implements Runnable {public void run() {// 加锁，拥有lock的Monitorsynchronized (lock) {// 获取lock的锁，然后进行通知，通知时不会释放lock的锁，// 直到当前线程释放了lock后，WaitThread才能从wait方法中返回System.out.println(Thread.currentThread()+ " hold lock. notify @ "+ new SimpleDateFormat("HH:mm:ss").format(new Date()));lock.notifyAll();flag = false;try {Thread.currentThread().sleep(5000l);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}// 再次加锁synchronized (lock) {System.out.println(Thread.currentThread()+ " hold lock again. sleep@ "+ new SimpleDateFormat("HH:mm:ss").format(new Date()));try {Thread.currentThread().sleep(5000l);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}}

运行结果：

Thread[WaitThread,5,main] flag is true. wait@ 15:33:26Thread[NotifyThread,5,main] hold lock. notify @ 15:33:27Thread[NotifyThread,5,main] hold lock again. sleep@ 15:33:32Thread[WaitThread,5,main] flag is false. running@ 15:33:37

0 0