Java的消费者/生产者

问题描述：

public class Queue { 
    int value = 0; 
    boolean isEmpty = true; 
    public synchronized void put(int n){ 
     if (!isEmpty){ 
      try { 
       System.out.println("producer is waiting"); 
       wait(); 
      }catch (Exception e){ 
       e.printStackTrace(); 
      } 
     } 
     value += n; 
     isEmpty = false; 
     System.out.println("The number of products："+value); 
     notifyAll(); 
    } 
    public synchronized void get(){ 
     if (isEmpty){ 
      try{ 
       System.out.println("customer is waiting"); 
       wait(); 
      }catch (Exception e){ 
       e.printStackTrace(); 
      } 
     } 
     value --; 
     if(value<1){ 
      isEmpty = true; 
     } 
     System.out.println("there are "+value+" left"); 
     notifyAll(); 
    } 
} 


public class Producer extends Thread{ 
    private Queue queue; 
    public Producer(String name,Queue queue){ 
     super(name); 
     this.queue = queue; 
    } 

    @Override 
    public void run() { 
     for (int i = 0; i < 5; i++) { 
      queue.put(i+1); 
     } 
    } 

} 

public class Producer extends Thread{ 
    private Queue queue; 
    public Producer(String name,Queue queue){ 
     super(name); 
     this.queue = queue; 
    } 

    @Override 
    public void run() { 
     for (int i = 0; i < 5; i++) { 
      queue.put(i+1); 
     } 
    } 
} 


public class Main { 

    public static void main(String[] args) { 
     Queue queue = new Queue(); 
     Thread customer1 = new Customer("customer1",queue); 
     Thread producer1 = new Producer("producer1",queue); 
     customer1.setPriority(4); 
     producer1.setPriority(7); 
     producer1.start(); 
     customer1.start(); 

    } 

}

输出：Java的消费者/生产者

 
The number of products：1  
producer is waiting  
there are 0left  
customer is waiting  
The number of products：2  
producer is waiting  
there are 1left  
there are 0left  
customer is waiting  
The number of products：3  
producer is waiting  
there are 2left  
there are 1left  
there are 0left  
customer is waiting 
The number of products：4  
producer is waiting  
there are 3left  
there are 2left  
there are 1left  
there are 0left  
customer is waiting  
The number of products：5  
there are 4left  
there are 3left  
there are 2left  
there are 1left  
there are 0left  
customer is waiting

我不知道为什么的输出顺序是这样的。

为什么它不在输出像

 
The number of products：3 
producer is waiting  
there are 2left  
The number of products: 6  
there are 5left    
The number of products: 10  
there are 9left  
The number of products: 15   
there are 14left

为什么您需要多线程？ – Professor901

我只是想知道为什么它不能这样工作。 –

过程同步不保证。 –

答

的结果，我认为这个问题是你不beeing通知后，请检查你的病情。

你做

if (condition){ 
    wait(); 
} 
increment();

虽然你的线程可能会在别的方面得到通知，也不会检查，如果条件仍然存在，或由另一个线程已经解决，做增量反正。正确的方法是在唤醒时重新检查您的状况，如：

while (condition){ 
    wait(); 
} 
increment();

Java的消费者/生产者

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