PRODUCER CONSUMER

                                                                     
                                                                     
                                                                     
                                             
Producer Consumer Problem:

/*To avoid polling, Java includes an elegant interprocess communication mechanism via the wait( ), notify( ), and notifyAll( ) methods. These methods are implemented as final methods in Object, so all classes have them. All three methods can be called only from within a synchronized method. Although conceptually advanced from a computer science perspective, the rules for using these methods are actually quite simple:
1) wait( ) tells the calling thread to give up the monitor and go to sleep until some other thread enters the same monitor and calls notify( ).    
2) notify( ) wakes up the first thread that called wait( ) on the same object.     
3) notifyAll( ) wakes up all the threads that called wait( ) on the same object. The highest priority thread will run first.*/

class Q
{
  int n;
  boolean valueSet = false;

  synchronized int get()
{
    if(!valueSet)
      try {
        wait();
}
catch(InterruptedException e)
     {
        System.out.println("InterruptedException caught");
      }
      System.out.println("Got: " + n);
      valueSet = false;
       notify();
              return n;
  }
  synchronized void put(int n) {
    if(valueSet)
      try {
        wait();
      } catch(InterruptedException e) {
        System.out.println("InterruptedException caught");
      }

      this.n = n;
      valueSet = true;
      System.out.println("Put: " + n);
      notify();
  }
}


class Producer implements Runnable {
  
Q q;

  Producer(Q q) {
    this.q = q;
    new Thread(this, "Producer").start();
  }

  public void run() {
    int i = 0;

    while(true) {
      q.put(i++);
    }
  }
}

class Consumer implements Runnable {
  Q q;

  Consumer(Q q) {
    this.q = q;
    new Thread(this, "Consumer").start();
  }

  public void run() {
    while(true) {
      q.get();
    }
  }
}

class prodcon {
  public static void main(String args[]) {
    Q q = new Q();
    new Producer(q);
    new Consumer(q);

    System.out.println("Press Control-C to stop.");
  }
}

/*inside get( ), wait( ) is called. This causes its execution to suspend until the Producer notifies you that some data is ready. When this happens, execution inside get( ) resumes. After the data has been obtained, get( ) calls notify( ). This tells Producer that it is okay to put more data in the queue. Inside put( ), wait( ) suspends execution until the Consumer has removed the item from the queue. When execution resumes, the next item of data is put in the queue, and notify( ) is called. This tells the Consumer that it should now remove it.*/