等待和通知

Object對象提供了wait( ) 方法和 notify ( ) 方法。

wait( )方法需要配對著synchronized 關鍵字使用。

當一個線程的資源調用 wait( )方法時，它會失去鎖，然後進入等待序列。

當其他線程調用notify方法時才會重新激活。

實例：

package com.xm.thread.t_19_01_27;

import java.util.concurrent.TimeUnit;

public class NotifyAndWait{

    private static Object object = new Object();


    static class WaitThread extends Thread{

        @Override
        public void run() {
            System.out.println("WaitThread Start!");
            try {
                System.out.println("Object wait!!!");
                synchronized (object) {
                    object.wait();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("WaitThread Finish!");
        }
    }

    static class NotifyThread extends Thread{

        @Override
        public void run() {
            System.out.println("NotifyThread Start!");
            System.out.println("Object notify");
            synchronized (object) {
                object.notify();
            }
            System.out.println("NotifyThread Finish!");
        }
    }



    public static void main(String[] args) throws InterruptedException {
        new WaitThread().start();

        TimeUnit.SECONDS.sleep(5);

        new NotifyThread().start();

    }
}


 

運行結果：

WaitThread Start!

Object wait!!!

NotifyThread Start!

Object notify

NotifyThread Finish!

WaitThread Finish!

notify( )方法只會隨機激活等待序列中的一個線程，而notifyAll( )方法激活所有等待的線程。

實例：

package com.xm.thread.t_19_01_27;

import java.util.concurrent.TimeUnit;

public class NotifyAndWait{

    private static Object object = new Object();


    static class WaitThread extends Thread{

        @Override
        public void run() {
            System.out.println("WaitThread Start!");
            try {
                System.out.println("Object wait!!!");
                synchronized (object) {
                    object.wait();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("WaitThread Finish!");
        }
    }

    static class NotifyThread extends Thread{

        @Override
        public void run() {
            System.out.println("NotifyThread Start!");
            System.out.println("Object notify");
            synchronized (object) {
                object.notify();
            }
            System.out.println("NotifyThread Finish!");
        }
    }



    public static void main(String[] args) throws InterruptedException {
        new WaitThread().start();

        new WaitThread().start();

        TimeUnit.SECONDS.sleep(5);

        new NotifyThread().start();

    }
}


 

運行結果：

WaitThread Start!

Object wait!!!

WaitThread Start!

Object wait!!!

NotifyThread Start!

Object notify

NotifyThread Finish!

WaitThread Finish!

結果分析：

兩個WaitThread線程只被喚醒了一個。

實例：

package com.xm.thread.t_19_01_27;

import java.util.concurrent.TimeUnit;

public class NotifyAndWait{

    private static Object object = new Object();


    static class WaitThread extends Thread{

        @Override
        public void run() {
            System.out.println("WaitThread Start!");
            try {
                System.out.println("Object wait!!!");
                synchronized (object) {
                    object.wait();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("WaitThread Finish!");
        }
    }

    static class NotifyThread extends Thread{

        @Override
        public void run() {
            System.out.println("NotifyThread Start!");
            System.out.println("Object notify");
            synchronized (object) {
                object.notifyAll();
            }
            System.out.println("NotifyThread Finish!");
        }
    }



    public static void main(String[] args) throws InterruptedException {
        new WaitThread().start();

        new WaitThread().start();

        TimeUnit.SECONDS.sleep(5);

        new NotifyThread().start();

    }
}


 

運行結果：

WaitThread Start!

Object wait!!!

WaitThread Start!

Object wait!!!

NotifyThread Start!

Object notify

NotifyThread Finish!

WaitThread Finish!

WaitThread Finish!

結果分析：

notifyAll( )方法會喚醒處在等待序列中的所有線程。

4.等待和通知