Java notifyAll() 唤醒所有线程

Object notifyAll() 方法用于唤醒在该对象上等待的所有线程。

notifyAll() 方法跟 notify() 方法一样，区别在于 notifyAll() 方法唤醒在此对象监视器上等待的所有线程，notify() 方法是一个线程。

如果当前线程不是对象监视器的所有者，那么调用 notifyAll() 方法同样会发生 IllegalMonitorStateException 异常。

语法

public final void notifyAll()

实例：

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
 
public class Test {
 
    private List synchedList;
 
    public Test() {
        // 创建一个同步列表
        synchedList = Collections.synchronizedList(new LinkedList());
    }
 
    // 删除列表中的元素
    public String removeElement() throws InterruptedException {
        synchronized (synchedList) {
 
            // 列表为空就等待
            while (synchedList.isEmpty()) {
                System.out.println("List is empty...");
                synchedList.wait();
                System.out.println("Waiting...");
            }
            String element = (String) synchedList.remove(0);
 
            return element;
        }
    }
 
    // 添加元素到列表
    public void addElement(String element) {
        System.out.println("Opening...");
        synchronized (synchedList) {
 
            // 添加一个元素，并通知元素已存在
            synchedList.add(element);
            System.out.println("New Element:'" + element + "'");
 
            synchedList.notifyAll();
            System.out.println("notifyAll called!");
        }
        System.out.println("Closing...");
    }
 
    public static void main(String[] args) {
        final Test demo = new Test();
 
        Runnable runA = new Runnable() {
 
            public void run() {
                try {
                    String item = demo.removeElement();
                    System.out.println("" + item);
                } catch (InterruptedException ix) {
                    System.out.println("Interrupted Exception!");
                } catch (Exception x) {
                    System.out.println("Exception thrown.");
                }
            }
        };
 
        Runnable runB = new Runnable() {
 
            // 执行添加元素操作，并开始循环
            public void run() {
                demo.addElement("Hello!");
            }
        };
 
        try {
            Thread threadA1 = new Thread(runA, "Google");
            threadA1.start();
 
            Thread.sleep(500);
 
            Thread threadA2 = new Thread(runA, "catroom");
            threadA2.start();
 
            Thread.sleep(500);
 
            Thread threadB = new Thread(runB, "Taobao");
            threadB.start();
 
            Thread.sleep(1000);
 
            threadA1.interrupt();
            threadA2.interrupt();
        } catch (InterruptedException x) {
        }
    }
}

以上程序执行结果为：

List is empty...
List is empty...
Opening...
New Element:'Hello!'
notifyAll called!
Closing...
Waiting...
Waiting...
List is empty...
Hello!
Interrupted Exception!