
sleep()是Thread的方法,wait()是Object的方法
如果线程进入了同步锁,sleep不会释放对象锁,wait会释放对象锁
sleep的作用就是让正在执行的线程主动让出CPU,给其它线程获得CPU的机会,在sleep指定的时间之后,CPU才会回到这个线程上继续往下执行,当线程进入了同步锁时,当别的线程也需要被加锁的资源时,sleep方法即使让出了CPU,别的线程也无法执行,因为无法获得锁。
wait方法是指在一个已经进入了同步锁的线程内,让自己暂时让出同步锁给别的线程用,只有等其他线程调用了notify或notifyAll方法后,才能去获得同步锁继续执行,需要注意的是,notify并不会释放锁,只是告诉调用过wait方法的线程可以去争取锁了,而不是马上得到锁。
此外在使用wait,notify,notifyAll方法的时候,要注意只能使用对象锁的持有者,即被*的对象来调用,不然会出IllegalMonitorStateException异常。
package javaBase;
/**
* sleep()和wait()的区别
* sleep()是Thread的方法,wait()是Object的方法
* sleep不会释放*的资源,wait会释放*的资源
* @author cnxno1
*
*/
public class JB_047_SleepAndWait {
public static void main(String[] args) {
Thread thread1 = new Thread(new Thread1());
Thread thread2 = new Thread(new Thread2());
thread1.start(); try {
System.out.println("延迟5秒启动线程2");
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
} thread2.start();
}
}
/**
* 公共资源类
* @author cnxno1
*
*/
class Resource{
public static String resource = "public resource";
}
/**
* 调用wait方法的线程
* @author cnxno1
*
*/
class Thread1 implements Runnable{
@Override
public void run(){
synchronized(Resource.resource){
System.out.println("this is thread1 , i hava the "+Resource.resource);
System.out.println("this is thread1 , i'm waiting the "+Resource.resource);
try{
Resource.resource.wait();
}catch(InterruptedException e){
e.printStackTrace();
}
System.out.println("this is thread1, i will going on...");
System.out.println("this is the end of thread1.");
}
}
} /**
* 调用sleep方法的线程
* @author cnxno1
*
*/
class Thread2 implements Runnable{
@Override
public void run(){
synchronized(Resource.resource){
System.out.println("this is thread2 , i'm notifyAll thread...");
Resource.resource.notifyAll();
System.out.println("this is thread2 , i will sleep 10 seconds...");
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("this is thread2, i will going on...");
System.out.println("this is the end of thread2.");
}
}
}
运行的结果如下:
延迟5秒启动线程2
this is thread1 , i hava the public resource
this is thread1 , i'm waiting the public resource
this is thread2 , i'm notifyAll thread...
this is thread2 , i will sleep 10 seconds...
this is thread2, i will going on...
this is the end of thread2.
this is thread1, i will going on...
this is the end of thread1.
可以看到thread1在调用了wait方法之后,thread2获得了同步锁,但是在thread2调用了sleep方法后,thread1并没有获得同步锁执行下去,而是在thread2 sleep了10秒执行完之后才获得了Resource.resource的锁得以执行完成。