sleep()和wait()有什么区别?

• sleep() 是 Thread 类的静态本地方法；wait() 是Object类的成员本地方法
• sleep() 方法可以在任何地方使用；wait() 方法则只能在同步方法或同步代码块中使用，否则抛出异常Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
• sleep() 会休眠当前线程指定时间，释放 CPU 资源，不释放对象锁，休眠时间到自动苏醒继续执行；wait() 方法放弃持有的对象锁，进入等待队列，当该对象被调用 notify() / notifyAll() 方法后才有机会竞争获取对象锁，进入运行状态
• JDK1.8 sleep() wait() 均需要捕获 InterruptedException 异常

测试代码

public class TestWaitSleep { private static Object obj = new Object();public static void main(String[] args) {//测试sleep()//测试 RunnableImpl1 wait(); RunnableImpl2 notify()Thread t1 = new Thread(new RunnableImpl1(obj));Thread t2 = new Thread(new RunnableImpl2(obj));t1.start();t2.start();//测试RunnableImpl3 wait(long timeout)方法Thread t3 = new Thread(new RunnableImpl3(obj));t3.start();} } class RunnableImpl1 implements Runnable { private Object obj;public RunnableImpl1(Object obj) {this.obj = obj;}public void run() {System.out.println("run on RunnableImpl1");synchronized (obj) {System.out.println("obj to wait on RunnableImpl1");try {obj.wait();} catch (InterruptedException e) {e.printStackTrace();}System.out.println("obj continue to run on RunnableImpl1");}}} class RunnableImpl2 implements Runnable { private Object obj;public RunnableImpl2(Object obj) {this.obj = obj;}public void run() {System.out.println("run on RunnableImpl2");System.out.println("睡眠3秒...");try {Thread.sleep(3000);} catch (InterruptedException e) {e.printStackTrace();}synchronized (obj) {System.out.println("notify obj on RunnableImpl2");obj.notify();}}} class RunnableImpl3 implements Runnable { private Object obj;public RunnableImpl3(Object obj) {this.obj = obj;}public void run() {System.out.println("run on RunnableImpl3");synchronized (obj) {System.out.println("obj to wait on RunnableImpl3");try {obj.wait(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("obj continue to run on RunnableImpl3");}}}

打印结果

run on RunnableImpl2睡眠3秒...run on RunnableImpl1obj to wait on RunnableImpl1run on RunnableImpl3obj to wait on RunnableImpl3obj continue to run on RunnableImpl3notify obj on RunnableImpl2obj continue to run on RunnableImpl1