1 sleep()介绍
sleep()定义在Thread.java中
sleep()的作用是让当前线程休眠,即当前线程会从"运行状态"进入到"休眠(阻塞)状态。sleep()会指定休眠时间,线程休眠的时间会大于/等于该休眠时间;在线程重新被唤醒时,它会由阻塞状态变成就绪状态,从而等于cpu的调度执行
2 sleep()示例
package com.tuhu.filt.javadatasleep;
public class SleepTest {
public static void main(String[] args) {
ThreadC t1 = new ThreadC("t1");
t1.start();
}
}
class ThreadC extends Thread{
public ThreadC (String name){
super(name);
}
public synchronized void run(){
try{
for (int i = 0;i < 10;i++) {
System.out.printf("%s: %d\n", this.getName(), i);
if( i%4 ==0){
Thread.sleep(100);
}
}
}catch (InterruptedException e){
e.printStackTrace();
}
}
}
程序比较简单在主线程main中启动线程t1.t1启动之后,当t1中的计算能被4整除时,t1会通过Thread.sleep(100)休眠100毫秒
3 sleep()与 wait()
wait 让当前线程由运行状态进入到等待阻塞状态 会释放同步锁
sleep 让当前线程由运行状态进入休眠阻塞状态 不会释放同步锁
下面通过示例演示sleep()是不会释放的
package com.tuhu.filt.javadatasleep;
// SleepLockTest.java的源码
public class SleepLockTest{
private static Object obj = new Object();
public static void main(String[] args){
ThreadA t1 = new ThreadA("t1");
ThreadA t2 = new ThreadA("t2");
t1.start();
t2.start();
}
static class ThreadA extends Thread{
public ThreadA(String name){
super(name);
}
public void run(){
// 获取obj对象的同步锁
synchronized (obj) {
try {
for(int i=0; i <10; i++){
System.out.printf("%s: %d\n", this.getName(), i);
// i能被4整除时,休眠100毫秒
if (i%4 == 0)
Thread.sleep(100);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
这和上一篇一个东西差不多,主线程main中启动了两个线程t1 和 t2 ,他们会引用同一个对象的同步锁,即synchronized(obj),在t1运行过程中,虽然他会调用Thread.sleep(100);但是t2是不会获取cpu执行权的。因为t1没有释放同步锁 注释掉synchronized(obj)后再次执行该程序t1和t2是可以相互切换的。比如用this
package com.tuhu.filt.javadatasleep;
// SleepLockTest.java的源码
public class SleepLockTest{
// private static Object obj = new Object();
public static void main(String[] args){
ThreadA t1 = new ThreadA("t1");
ThreadA t2 = new ThreadA("t2");
t1.start();
t2.start();
}
static class ThreadA extends Thread{
public ThreadA(String name){
super(name);
}
public void run(){
// 获取obj对象的同步锁
synchronized (this) {
try {
for(int i=0; i <10; i++){
System.out.printf("%s: %d\n", this.getName(), i);
// i能被4整除时,休眠100毫秒
if (i%4 == 0)
Thread.sleep(100);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}