等待并通知Java中的死锁情况

线程t1在wait()被命中后进入死锁。即使在t2中有notify()。代码正陷入僵局。没有得到打印声明 - “等待释放后::::”等待并通知Java中的死锁情况

我可以看到两个线程竞争获取显示器counterAdd()。所以，我假设通知会起作用。

package com.java.thread.practice; 

    public class WaitAndNotify4 { 

     int counter = 0; 

     /* 
      CounterAdd() is to be accessed by both t1 and t2. 
      If not synchronized not giving consistent output. 
     */ 
     synchronized int counterAdd(){ 
      return counter++; 
     } 

     public static void main(String[] args) throws InterruptedException{ 

      // Creating method to call the threads. 
      WaitAndNotify4 andNotify4 = new WaitAndNotify4(); 
      andNotify4.testRaceCondition(); 

     } 

     private void testRaceCondition() throws InterruptedException { 

      // Thread t1 created and launched. 

      Thread t1 = new Thread(new Runnable(){ 
       @Override 
       public void run() { 

        for(int i=0; i<5; i++){ 
         synchronized(this){ 
         if(i== 1){ 
          System.out.println("Calling wait after count 1"); 
          try { 
          // Assuming that this wait will be resumed by notify in t2. 

           wait(); 
           System.out.println("After wait is released :::: "); 
          } catch (InterruptedException e) { 
           // TODO Auto-generated catch block 
           e.printStackTrace(); 
          } 

         } 
         } 
         counterAdd(); 
        } 
       } 
      }); 


      Thread t2 = new Thread(new Runnable(){ 
       @Override 
       public void run() { 
        // TODO Auto-generated method stub 

        for(int i=0; i<5; i++){ 
         if(i==2){ 

          synchronized(this){ 
           System.out.println("Before releasing the counter :::::"); 
           notify(); 
           System.out.println("After releasing the counter :::::"); 
          } 

         } 
         counterAdd(); 
        } 

       } 
      }); 



      t1.start(); 
      t2.start(); 

      t1.join(); 
      t2.join(); 

      System.out.println(" Sum value is found as ::::: "+counter); 

     } 
    }

来源

2017-02-17 Ravi_Kumar

不要对没有引用的文本使用引号格式。 – EJP

正在同步于不同的对象。在对象t1的第一种情况下，在t2的第二种情况下，在方法counterAdd的andNotify4中。为了永久锁定andNotify4，你需要做这样的事情。

public class Main { 
    private int counter = 0; 

    synchronized int counterAdd() { 
     return counter++; 
    } 

    public static void main(String[] args) throws InterruptedException { 
     Main andNotify4 = new Main(); 
     andNotify4.testRaceCondition(); 
    } 

    private void testRaceCondition() throws InterruptedException { 
     Thread t1 = new Thread(new Runnable() { 
      @Override 
      public void run() { 
       for (int i = 0; i < 5; i++) { 
        synchronized (Main.this) { 
         if (i == 1) { 
          System.out.println("Calling wait after count 1"); 
          try { 
           Main.this.wait(); 
           System.out.println("After wait is released :::: "); 
          } catch (InterruptedException e) { 
           e.printStackTrace(); 
          } 
         } 
        } 
        counterAdd(); 
       } 
      } 
     }); 

     Thread t2 = new Thread(new Runnable() { 
      @Override 
      public void run() { 
       for (int i = 0; i < 5; i++) { 
        if (i == 2) { 
         synchronized (Main.this) { 
          System.out.println("Before releasing the counter :::::"); 
          Main.this.notify(); 
          System.out.println("After releasing the counter :::::"); 
         } 
        } 
        counterAdd(); 
       } 
      } 
     }); 

     t1.start(); 
     t2.start(); 

     t1.join(); 
     t2.join(); 

     System.out.println(" Sum value is found as ::::: " + counter); 
    } 
}

来源

2017-02-17 08:53:30 Divers

非常感谢。它解决了问题并清除了这个概念。如果你还可以对部分内容有所了解。 “ 我可以看到两个线程竞争获取counterAdd（）中的监视器，因此，我认为通知将起作用。” –

如果它们是参考不同对象的两个不同线程，counterAdd（）应该总是打印10总是没有同步关键字。 –

等待并通知Java中的死锁情况

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