ReentrantLock 没有给出预期的结果

Question

我使用线程（等待和通知）功能创建了一个生产者消费者程序。代码是-

/**
 *  Message.java ( Common object )
 */
package threads;

import java.util.concurrent.locks.ReentrantLock;

/**
 * @author chouhan_r
 *
 */
public class Message {
    private String message;

    ReentrantLock lock = new ReentrantLock();
    ReentrantLock takelock = new ReentrantLock();
    private boolean empty =true;
    public  void put(String message){
        lock.lock();
        while(!empty){
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        empty = false;
        this.message = message;

        notifyAll();
        lock.unlock();
    }

    public String take(){

        takelock.lock();
        while(empty){
            try {
                wait();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        empty = true;

        notifyAll();
        takelock.unlock();
        return message;

    }


}


/**
 * Producer.java
 */
package threads;

import java.util.Random;

public class Producer implements Runnable{
    private Message message;
    public Producer(Message message) {
        this.message = message;
    }

    @Override
    public void run() {
        String[] impInfo = {"Hello", "I am here", "why are you doing this ??", "No problem" };
        Random random = new Random();
        for(String str : impInfo){
            message.put(str);
            try {
                Thread.sleep(random.nextInt(3000));
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        message.put("Finished");

    }



}

/**
 * Consumer.java
 */
package threads;

public class Consumer implements Runnable{
    private Message message;
    public Consumer(Message message) {
        this.message = message;
    }
    @Override
    public void run() {
        System.out.println(message);
        String msg = message.take();
        while(!"Finished".equalsIgnoreCase(msg)){
            System.out.println(msg);
            msg = message.take();
        }


    }


}

=====================

/**
 * Main Program
 */
package threads;

public class ProConsTest {

    public static void main(String[] args) {
        Message message = new Message();
        new Thread(new Consumer(message)).start();
        new Thread(new Producer(message)).start();



    }

}

我正在尝试使用 ReentrantLock 执行此代码，但它给我以下错误 -

Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
    at java.lang.Object.wait(Native Method)
    at java.lang.Object.wait(Unknown Source)
    at threads.Message.take(Message.java:39)
    at threads.Consumer.run(Consumer.java:11)
    at java.lang.Thread.run(Unknown Source)
Exception in thread "Thread-1" java.lang.IllegalMonitorStateException
    at java.lang.Object.notifyAll(Native Method)
    at threads.Message.put(Message.java:31)
    at threads.Producer.run(Producer.java:16)
    at java.lang.Thread.run(Unknown Source)

我是不是做错了什么？？当我将 Message.java 中的方法标记为同步时，它工作得很好。我们可以运行此代码仅使用可重入锁吗？？

Answer 1

Object.wait 和 Object.notify 连接到内部锁定功能，与 synchronized 块和方法一起使用。

如果要用Locks，这两种方法就不能用了。相反，您必须在同一个 Condition 实例上 create a Condition and call await() on it, which should be paired with another thread calling signal()。请注意，与 Object.wait 和 Object.notify 不同，每个 Lock 可以有多个 Condition 并且等待特定条件的线程将被调用 [=24= 的线程唤醒] 在同一个 Condition 实例上。

但是，与内在锁定功能一样，在 Condition 上调用方法之前，您必须拥有关联的锁。如果是 ReadWriteLock，您必须拥有写锁。

不幸的是，Conditions 从 Object 继承了方法 wait 和 notify，因此切勿将它们混淆，这需要特别小心，因为很难区分名字，wait 和 await.

documentation of Condition 包含一个完整的示例。我只是选择了一个代码片段来说明 put 方法中的用法：

final Lock lock = new ReentrantLock();
final Condition notFull  = lock.newCondition(); 
final Condition notEmpty = lock.newCondition();

…

lock.lock();
try {
  while (count == items.length)
    notFull.await();
  items[putptr] = x;
  if (++putptr == items.length) putptr = 0;
  ++count;
  notEmpty.signal();
} finally {
  lock.unlock();
}

ReentrantLock 没有给出预期的结果

ReentrantLock not giving expected result

java

concurrency

locking