Java Thread Tutorial - Java Thread Producer/Consumer

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The producer/consumer is a typical thread synchronization problem that uses the wait() and notify() methods.

Example

There are four classes: Buffer, Producer, Consumer, and ProducerConsumerTest.

An object of the Buffer class has an integer data element that will be produced by the producer and consumed by the consumer.

We have to synchronize the access to the buffer, so the Producer produces a new data element only when the Buffer is empty and the Consumer consumes the buffer's data only when it is available.

The ProducerConsumerTest class is used to test the program.

import java.util.Random;
/*w w w.  j a  v a  2s. c o m*/
class Consumer extends Thread {
  private Buffer buffer;

  public Consumer(Buffer buffer) {
    this.buffer = buffer;
  }

  public void run() {
    int data;
    while (true) {
      data = buffer.consume();
    }
  }
}

public class Main {
  public static void main(String[] args) {
    Buffer buffer = new Buffer();
    Producer p = new Producer(buffer);
    Consumer c = new Consumer(buffer);

    p.start();
    c.start();
  }
}

class Producer extends Thread {
  private Buffer buffer;

  public Producer(Buffer buffer) {
    this.buffer = buffer;
  }

  public void run() {
    Random rand = new Random();
    while (true) {
      int n = rand.nextInt();
      buffer.produce(n);
    }
  }
}

class Buffer {
  private int data;
  private boolean empty;

  public Buffer() {
    this.empty = true;
  }

  public synchronized void produce(int newData) {
    while (!this.empty) {
      try {
        this.wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    this.data = newData;
    this.empty = false;
    this.notify();
    System.out.println("Produced:" + newData);
  }

  public synchronized int consume() {
    while (this.empty) {
      try {
        this.wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    this.empty = true;
    this.notify();
    System.out.println("Consumed:" + data);
    return data;
  }
}

The code above generates the following result.

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