java - Notify()不与Wait()一起使用

我是线程和学习的新手，但是在下面的代码中，为什么notify不起作用。根据我的理解，当i = 5时，notify应该执行主线程并打印总数。如果我错了，请纠正。

public class ThreadA {
public static void main(String[] args){
    ThreadB b = new ThreadB();
    b.start();

    synchronized(b){
        try{
            System.out.println("Waiting for b to complete...");
            b.wait();
        }catch(InterruptedException e){
            e.printStackTrace();
        }

        System.out.println("Total is: " + b.total);
    }
}
}

class ThreadB extends Thread{
    int total;
    @Override
    public void run(){
        synchronized(this){
            for(int i=0; i<10 ; i++){
                total += i;
             if(i==5){
                 System.out.println("Notify");
                 notify();
                 }
                System.out.println("Total is in cal thread: "+i+":" + total);
            }

        }
    }
}

这是程序的输出：

Waiting for b to complete...
Total is in cal thread: 0:0
Total is in cal thread: 1:1
Total is in cal thread: 2:3
Total is in cal thread: 3:6
Total is in cal thread: 4:10
Notify
Total is in cal thread: 5:15
Total is in cal thread: 6:21
Total is in cal thread: 7:28
Total is in cal thread: 8:36
Total is in cal thread: 9:45
Total is: 45 –

最佳答案

synchronized(b){
    try{
        System.out.println("Waiting for b to complete...");
        b.wait();

调用notify仅影响当前正在等待的线程，在调用之后开始等待的线程将不受影响。在您可以100％确认同步块内尚未等待的事情之前，请不要调用wait。