import java.util.*;

// same as ProducerConsumer with one change.  The Consumer now will yield its time (using yield) 
// if it tries to consume an element in buffer that has not yet been produced.  This is the case if front>=rear.
public class ProducerConsumer2
{
	private static int[] buffer;
	private static int front, rear;
	private static Random g;
	private static Thread t1, t2, t3, t4, t5;
	private static boolean done;
	
	public static void main(String[] args)
	{
		buffer=new int[10];
		front=0;
		rear=0;
		g=new Random();
		done=false;
		Producer p1=new Producer("Producer 1");
		Producer p2=new Producer("Producer 2");
		Consumer c1=new Consumer("Consumer 1");
		Consumer c2=new Consumer("Consumer 2");
		Consumer c3=new Consumer("Consumer 3");	
		t1=new Thread(p1);
		t2=new Thread(p2);
		t3=new Thread(c1);
		t4=new Thread(c2);
		t5=new Thread(c3);
		t1.start();
		t2.start();
		t3.start();
		t4.start();
		t5.start();		
	}
	
	
	public static class Producer implements Runnable
	{
		private String name;
		public Producer(String name){
			this.name=name;
		}
		public void run()
		{
			int temp;
			while(!done)
			{
				try{
					temp=g.nextInt(1000);
					System.out.println(name + " sleeping for " + temp);
					Thread.sleep(temp);
				}
				catch(InterruptedException e) {
					System.out.println(e);
				}
				temp=g.nextInt(10)+1;
				System.out.println("Producer " + name + " producing " + temp + " at " + rear);
				buffer[rear]=temp;
				rear++;								
			}
		}
	}

	public static class Consumer implements Runnable
	{
		private String name;
		public Consumer(String name){
			this.name=name;
		}
		public void run()
		{
			int temp;
			while(!done)
			{
				try{
					temp=g.nextInt(1000);
					System.out.println(name + " sleeping for " + temp);
					Thread.sleep(temp);
				}
				catch(InterruptedException e)
				{
					System.out.println(e);
				}
				if(front>=rear) {		// if true, we have consumed more than has been produced, must wait
					System.out.println(name + " attempting to consume empty list, forced to yield");  // inform user
					try{
						if(g.nextInt(2)==1) t1.join();
						else t2.join();
					}
					catch(InterruptedException e)
					{
						System.out.println(e);
					}
				}
				temp=buffer[front];
				System.out.println("Consumer " + name + " consuming " + temp + " at " + front);
				front++;								
			}
		}
	}	
}

// running this program will show that no Consumer will consume a value of 0 but it does not fix the problem
// of a Producer placing a value into a buffer in the wrong location (once rear >= 10)