java - 并行执行线程超时

Question

处理并行线程时，输出应该是:“wait，done”!目前它是:“等等，不应该显示，完成”。有人可以帮忙吗？
我的主要:

public class Test {
    public static void main(String[] args) {
        Supervisor a = new Supervisor();
        System.out.println("done");
    }
}

类主任:

public class Supervisor {       
     public Supervisor()  { 
            Calculate t1 = new Calculate();
            t1.start(); 
            synchronized(t1){  
                System.out.println("wait");
                try {
                    t1.wait(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }           
        }   
    }
}

和计算器类:

public class Calculate extends Thread {
    public Calculate(){}

    @Override
    public void run() {
              synchronized(this){  
                  try {
                        Thread.sleep(10000);
                        System.out.println("not supposed to be shown");
                    } catch(InterruptedException ex) {
                         Thread.currentThread().interrupt();
                    }                   
                notify();
            }   
    }    
}

Answer 1

这段代码:

        t1.start(); 
        synchronized(t1){  

可能导致t1在synchronized部分之前run。像这样解决这个问题:

        synchronized(t1){  
          t1.start(); 

还有关于 sleep 的文档:

Causes the currently executing thread to sleep (temporarily cease execution) ...

使用此代码，事情看起来更清晰:

public class Calculate extends Thread {

    public Calculate() {
    }

    @Override
    public void run() {
        synchronized (this) {
            try {
                System.out.println("Calc sleeping");
                Thread.sleep(10000);
                System.out.println("not supposed to be shown");
            } catch (InterruptedException ex) {
                Thread.currentThread().interrupt();
            }
            notify();
        }
    }
}

public class Supervisor {

    public Supervisor() {
        Calculate t1 = new Calculate();
        System.out.println("Super " + Thread.currentThread().getName());
        synchronized (t1) {
            t1.start();
            System.out.println("wait");
            try {
                System.out.println("Super waiting");
                t1.wait(1000);
                System.out.println("Super awake");
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("finish");
        }
    }
}

打印:

Super main
wait
Super waiting
Calc sleeping
not supposed to be shown
Super awake
finish

看到，当 Supervisor hibernate 时，Calculate 被唤醒并运行完成，需要 10 秒，然后调用 notify 唤醒 Supervisor 继续。