java - 线程同步问题(更新变量总和)

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ReentrantLock doesn't work out
                                
                                    （1个答案）
                                
                        
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当我想使用synced关键字或lock更新时，当sum变量为int而不是Integer对象时，它可以工作。

代码看起来像这样-

public class TestSynchronized {
  private  Integer sum = new Integer(0);

  public static void main(String[] args) {
    TestSynchronized test = new TestSynchronized();
    System.out.println("The sum is :" + test.sum);
  }

  public TestSynchronized() {
    ExecutorService executor = Executors.newFixedThreadPool(1000);

    for (int i = 0; i <=2000; i++) {
      executor.execute(new SumTask());
    }

    executor.shutdown();

    while(!executor.isTerminated()) {
    }
  }

  class SumTask implements Runnable {
    Lock lock = new ReentrantLock();

    public void run() {
    lock.lock();

      int value = sum.intValue() + 1;
      sum = new Integer(value);

        lock.unlock(); // Release the lock
      }

  }
}

最佳答案

问题是您为每个locks对象都单独设置了SumTask。这些对象应该共享locks。

在lock方法中一次创建一个TestSynchronized()对象。这应该由所有new SumTask(lock)对象共享。

因此，您的SumTask类如下所示：

class SumTask implements Runnable {
    Lock lock;

    public SumTask(Lock commonLock) {
        this.lock = commonLock;
    }

    public void run() {
        lock.lock();

        int value = sum.intValue() + 1;
        sum = new Integer(value);

        lock.unlock(); // Release the lock
    }

}

并且不要忘记在commonLock方法中创建TestSynchronized()对象：

  Lock lock = new ReentrantLock();

  executor.execute(new SumTask(commonLock));