实例分析Java notifyAll方式的使用

java notifyAll()方法唤醒所有处于阻塞状态的线程继续执行阻塞后的代码逻辑。

/**

* 当方法wait()被执行后，锁被自动释放，但是执行完notify()方式，锁却不自动释放

**/

class ServiceWait {

public void testMethod(Object lock) {

try {

synchronized (lock) {

System.out.println(“begin wait start== ” + System.currentTimeMillis() + ” —ThreadName ” + Thread.currentThread().getName());

lock.wait();

System.out.println(“end wait == ” + System.currentTimeMillis() + ” —ThreadName ” + Thread.currentThread().getName());

}

} catch (InterruptedException e) {

e.toString();

}

}

}

class NotifyAllThread extends Thread {

private Object lock;

public NotifyAllThread(Object lock) {

super();

this.lock = lock;

}

@Override

public void run() {

synchronized (lock) {

lock.notifyAll();

}

}

}

class A extends Thread {

private Object lock;

public A(Object lock) {

super();

this.lock = lock;

}

@Override

public void run() {

ServiceWait serviceWait = new ServiceWait();

serviceWait.testMethod(lock);

}

}

class B extends Thread {

private Object lock;

public B(Object lock) {

super();

this.lock = lock;

}

@Override

public void run() {

ServiceWait serviceWait = new ServiceWait();

serviceWait.testMethod(lock);

}

}

class C extends Thread {

private Object lock;

public C(Object lock) {

super();

this.lock = lock;

}

@Override

public void run() {

ServiceWait serviceWait = new ServiceWait();

serviceWait.testMethod(lock);

}

}

public static void main(String[] args) {

Object lock = new Object();
A a = new A(lock);
a.start();
B b = new B(lock);
b.start();
C c = new C(lock);
c.start();
//等待一个时间，可以清晰看到，上面的线程一直处于阻塞状态
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
//执行通知线程
NotifyAllThread m = new NotifyAllThread(lock);
m.start();
}

}

代码执行结果：

begin wait start== 1469187894185 —ThreadName Thread-0 —–线程A执行run()方法，然后阻塞等待通知

begin wait start== 1469187894185 —ThreadName Thread-1—–线程B执行run()方法，然后阻塞等待通知

begin wait start== 1469187894185 —ThreadName Thread-2—–线程C执行run()方法，然后阻塞等待通知

等待2钟，然后通过线程NotifyAllThread来通知其他的线程继续执行。

end wait == 1469187896186 —ThreadName Thread-2

end wait == 1469187896187 —ThreadName Thread-1

end wait == 1469187896187 —ThreadName Thread-0