Consumer producer

Question

hi
iam learning Threads in java..i know its a simple question but can can anybody please explain me the concept, the flow
of control in the following example of consumer and producer?..as iam not very clear about it....iam interested to know how excatly interthread communication is taking place....
.how does while(true) executes....because for both producer thread and consumer thread the condition is checked with true....
class Queue
     int n;
     boolean valueset=false;
     synchronized public void put(int n)
          if(valueset)
          try{
               wait();
          }catch(InterruptedException e)
               System.out.println("Interrupted");
          this.n=n;
          valueset=true;
          System.out.println("Put: "+n);
          notify();
     synchronized int get()
               if(!valueset)
try
               wait();
          }catch(InterruptedException e)
               System.out.println("Interrupted");
          System.out.println("Got:"+n);
          valueset=false;
          notify();
          return n;
class Producer implements Runnable
     Queue q;
     public Producer(Queue q)
          this.q=q;
          //int i=0;
          new Thread(this,"Producer").start();
     public void run()
          int i=0;
          while(true)
               q.put(i++);
class Consumer implements Runnable
     Queue q;
     public Consumer(Queue q)
          this.q=q;
          new Thread(this,"Consumer").start();
     public void run()
          while(true)
               q.get();
class Conandpro
     public static void main(String args[])
          Queue q=new Queue();
          Producer p=new Producer(q);
          Consumer c=new Consumer(q);
          System.out.println("press control-c to stop");
}

Answer 1

When you post code, please use [code] and [/code] tags as described in Formatting Help on the message entry page. It makes it much easier to read and prevents accidental markup from array indices like [i].
Because your put() method is synchronized, a producer entering that method acquires a lock on Queue - no other threads can get in any synchronized method of Queue.
If the value has not been set, the producer adds a value and notifies any waiting threads that a value is available. If the value is already set, The Queue object calls wait() and releases the lock acquired by the producer, and - of course - waits to be notified. Since the lock has been released, the thread scheduler automagically wakes up another waiting thread; in this case, the consumer, who can then call get() and retrieve the value.
The consumer acts similarly, but with regards to the get() method.