Producer Consumer Problem trong Java

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Miêu tả vấn đề

Cách xử lý Producer Consumer Problem bởi sử dụng thread trong Java?

Giải pháp

Ví dụ sau minh họa cách xử lý Producer Consumer Problem bởi sử dụng thread trong Java.

public class ProducerConsumerTest {
   public static void main(String[] args) {
      CubbyHole c = new CubbyHole();
      Producer p1 = new Producer(c, 1);
      Consumer c1 = new Consumer(c, 1);
      p1.start(); 
      c1.start();
   }
}
class CubbyHole {
   private int contents;
   private boolean available = false;
   public synchronized int get() {
      while (available == false) {
         try {
            wait();
         }
         catch (InterruptedException e) {
         }
      }
      available = false;
      notifyAll();
      return contents;
   }
   public synchronized void put(int value) {
      while (available == true) {
         try {
            wait();
         }
         catch (InterruptedException e) { 
         } 
      }
      contents = value;
      available = true;
      notifyAll();
   }
}class Consumer extends Thread {
   private CubbyHole cubbyhole;
   private int number;
   public Consumer(CubbyHole c, int number) {
      cubbyhole = c;
      this.number = number;
   }
   public void run() {
      int value = 0;
         for (int i = 0; i < 10; i++) {
            value = cubbyhole.get();
            System.out.println("Consumer #" 
			+ this.number
+ " got: " + value);
}
}
}class Producer extends Thread {
private CubbyHole cubbyhole;
private int number;public Producer(CubbyHole c, int number) {
cubbyhole = c;
this.number = number;
}public void run() {
for (int i = 0; i < 10; i++) {
cubbyhole.put(i);
System.out.println("Producer #" + this.number
+ " put: " + i);
try {
sleep((int)(Math.random() * 100));
} catch (InterruptedException e) { }
}
}
}

Kết quả

Code trên sẽ cho kết quả sau:

Producer #1 put: 0
Consumer #1 got: 0
Producer #1 put: 1
Consumer #1 got: 1
Producer #1 put: 2
Consumer #1 got: 2
Producer #1 put: 3
Consumer #1 got: 3
Producer #1 put: 4
Consumer #1 got: 4
Producer #1 put: 5
Consumer #1 got: 5
Producer #1 put: 6
Consumer #1 got: 6
Producer #1 put: 7
Consumer #1 got: 7
Producer #1 put: 8
Consumer #1 got: 8
Producer #1 put: 9
Consumer #1 got: 9

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