Synchronizing thread woes!

[Rogelio Tristan]

heres my code (runs and compiles fine!)

 
import java.util.*;
 
class Counter
{
 private int count;
 public Counter()
 {
  count = 0;
 }
 
 public void increment()
 {
  ++count;
 }  
 
 public void decrement()
 {
  --count;
 }  
 
 public int get()
 {
  return count;
 }
}
 
class Queue
{
 static Queue store = new Queue();
 private LinkedList data = new LinkedList();
 public void put(Object o)
 {
  data.addFirst(o);
 }
 
 public Object get()
 {
  return data.removeLast();
 }
 
 public int size()
 {
  return data.size();
 }
}
 

class Producer extends Thread
{
 private static Random numbers = new Random();
 private Counter counter;
 
 Producer(String id, Counter counter)
 {
  super(id);
  this.counter = counter;
 }
 
 int genNumber()
 {
  return (int)(numbers.nextDouble()*1000);
 }
 
 public void run()
 {
  counter.increment();
  for(int i =0; i < 10; ++i)
  {
   int number = genNumber();
   System.out.println(getName()+ " producing " + number);
   synchronized(Queue.store)
   {
    Queue.store.put(new Integer(number));
    Queue.store.notify();
   }
  }
 
  synchronized(Queue.store)
  {
   counter.decrement();
   Queue.store.notifyAll();
  }
 System.out.println("\t" + getName() + " finished");
 }
}
 

class Consumer extends Thread
{
 private Counter counter;
 Consumer(String id, Counter counter)
 {
  super(id);
  this.counter = counter;
 }
 
 public void run()
 {
  for(; :wink: 
  {
   synchronized(Queue.store)
   {
    while(Queue.store.size() == 0)
    {
     if(counter.get() == 0)
     {
      System.out.println("\t" + getName() + " terminating");
      return;
     }
    try
     {
      Queue.store.wait();
     }
    catch(InterruptedException x)
     {
      
     }
    }
    System.out.println(getName() + " consuming" + Queue.store.get());
   }
  }
 }
}
 

public class CommTest1
{
 public static void main(String[] args)
 {
 Counter counter = new Counter();
  new Producer("Producer1", counter).start();
 
  new Consumer("Consumer1", counter).start();
  new Consumer("Consumer2", counter).start();
 }
} 

okay I figured out how to make a thread, and it puts numbers in a Queue, and then the consumer consumes the Queue. but my biggest problem is I need to have 2 consumers, one consumes 5, then the other consumes 5. how is that possible? I have thrown various counters in there but am still having quite some trouble, I'm not asking for just the answer, I'm asking for an explanation as to why the answer would be that. What do I do to make it comsume 5 first, then 5 to the next? any help is appreciated guys

[Henry Wong]

Step 1: Don't consuming anything until there is at least 5 items.

Change:

    while(Queue.store.size() == 0) {

To:

    while(Queue.store.size() < 5) {

Step 2: Consume 5 items without releasing the lock. I'll let you figure that out yourself.

[Rogelio Tristan]

okay I appreciate the help and letting me try to figure it out myself.. let me know if I am hot or cold okay.. I was thinking putting the

Queue.store.wait();

statement 5 times; when I did it did it 5 times, then passed it back to the producer, then it went into this endless loop. so thats not it.


this has to do with the insertion of a
Queue.store.notify();
statement am i correct? perhaps get it to wait for 5 threads, then use notify to wake up the other thread again... hmm...