Java 中 wait()、notify() 和 notifyAll() 方法的重要性?
线程可以通过 Java 中的 wait()、notify() 和 notifyAll() 方法相互通信。它们是 Object 类中定义的 final 方法,只能在同步上下文中调用。wait() 方法表示当前线程等待,直到另一个线程为此对象调用 notify() 或 notifyAll() 方法。
notify() 方法唤醒在该对象监视器上等待的单个线程。notifyAll() 方法唤醒在该对象监视器上等待的所有线程。线程通过调用其中一种 wait() 方法来等待对象监视器。如果当前线程不是对象监视器的所有者,则这些方法会引发 IllegalMonitorStateException。
wait() 方法语法
public final void wait() throws InterruptedException
notify() 方法语法
public final void notify()
notifyAll() 方法语法
public final void notifyAll()
示例
public class WaitNotifyTest { private static final long SLEEP_INTERVAL = 3000; private boolean running = true; private Thread thread; public void start() { print("Inside start() method"); thread = new Thread(new Runnable() { @Override public void run() { print("Inside run() method"); try { Thread.sleep(SLEEP_INTERVAL); } catch(InterruptedException e) { Thread.currentThread().interrupt(); } synchronized(WaitNotifyTest.this) { running = false; WaitNotifyTest.this.notify(); } } }); thread.start(); } public void join() throws InterruptedException { print("Inside join() method"); synchronized(this) { while(running) { print("Waiting for the peer thread to finish."); wait(); //waiting, not running } print("Peer thread finished."); } } private void print(String s) { System.out.println(s); } public static void main(String[] args) throws InterruptedException { WaitNotifyTest test = new WaitNotifyTest(); test.start(); test.join(); } }
输出
Inside start() method Inside join() method Waiting for the peer thread to finish. Inside run() method Peer thread finished.
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