多线程编程 java.lang.IllegalMonitorStateException at java.lang.Object.wait

[anlian523]

写两个线程，其中一个线程打印1-52，另一个打印A-Z，打印顺序为12A34B56C....5152Z。没有用同步方法或者同步代码块。用的lock和condition，还用了下线程池。不知道为什么报异常，它意思我在wait的时候没有获得锁，但实际要进入wait前肯定是获得锁了的呀，困惑中，代码如下求解答。

package testSix;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class Print
{
    private boolean flag = false;
    public int num = 1;
    public char chr = 'A';
    
    private final Lock lock=new ReentrantLock();
    private final Condition cond=lock.newCondition();
    
    public void printNumber()
    {
    	lock.lock();
        try
        {
            if(flag)
            {
                if(num <= 52)
                {
                    cond.wait();
                }
            }
            else
            {
            	//进入else进入了26次
                System.out.print(num);
                System.out.print(num + 1);
                num += 2;
                flag = true;
                cond.signalAll();
            }
        }
        catch(InterruptedException ie)
        {
            ie.printStackTrace();
        }
        finally
        {
        	lock.unlock();
        }
    }
     
    public void printWord()
    {
    	lock.lock();
        try
        {
            if(!flag)
            {
                if(chr <= 'Z')
                {
                    cond.await();
                }
            }
            else
            {
                System.out.print(chr);
                chr += 1;
                flag = false;
                cond.signalAll();
            }
        }
        catch(InterruptedException ie)
        {
            ie.printStackTrace();
        }
        finally
        {
        	lock.unlock();
        }
    }
}

package testSix;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;



public class printTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		Print p = new Print();
		ExecutorService service = Executors.newCachedThreadPool();  
		service.execute(()->{
            for(int i = 0; i < 52; i ++)
            {
                p.printNumber();
            }
        
             });
		service.execute(()->{
            for(int i = 0; i < 52; i ++)
            {
                p.printWord();
            }
        
             });
		
		
	}

}

[soton_dolphin]

那个红色正方形是“停止“钮””程序运行时会变红色，程序运行完就变灰红色

[anlian523]

12AException in thread "pool-1-thread-1" java.lang.IllegalMonitorStateException at java.lang.Object.wait(Native Method) at java.lang.Object.wait(Unknown Source) at testSix.Print.printNumber(Print.java:25) at testSix.printTest.lambda$1(printTest.java:28) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source) 实际上是先打印出来12A后，才开始报异常的

[soton_dolphin]

少了个a 啊，应该是if(num <= 52) { cond.await(); }

[anlian523]

引用 2 楼 soton_dolphin 的回复:

少了个a 啊，应该是if(num <= 52) { cond.await(); }

对哈，怪我不仔细了。改了就对了，运行结果对了，但是看见console那个红色正方形先亮了一会，然后就没了。说明是finally最终把锁释放了，所以最后没有阻塞吗？还有就是以下这段代码应该已经设置阻塞的终点，应该打印完就不会阻塞了啊？ if(flag) { if(num <= 51) { cond.await(); } }