无人notify的问题

<=20与<20不同的结果

 

public class PrintNum{private Object lock = new Object();public void test(){printThread p1 = new printThread("t1");printThread p2 = new printThread("t2");p1.start();p2.start();}public static void main(String[] args){PrintNum p = new PrintNum();p.test();}class printThread extends Thread{public printThread(String name){this.setName(name);}@Overridepublic void run(){synchronized (lock) {lock.notify();for(int i=1;i<=20;i++){if(i%10==0)try {lock.wait();} catch (InterruptedException e) {}System.out.println(this.getName()+" "+i);}}}}}