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Thread: working with multiple threads

  1. #1
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    Default working with multiple threads

    I'm trying to build a bank simulation using a queue, I got it to run but the results are not expected.
    i'm trying to have clients adding to a queue and Tellers serving them running for 2 minutes. After Client 2, for some reason the tellers are not running anymore. I know it's still running in the background but not doing anything. Can someone points me the problem. Thanks.
    HEre is the code

    import java.util.*;
    import java.io.*;
    import java.util.concurrent.*;
     
    //now with Tellers
     
    class banker3 implements Runnable
    {
    	public BlockingQueue<Client> bq = new LinkedBlockingQueue<Client>();
    	public static boolean stop = false;
    	private int arrival;
    	private static Random rand = new Random();
    	public banker3(BlockingQueue<Client> inq)
    	{
    		bq = inq;
    	}
     
    	public void run()
    	{
     
    		while(true)
    		try{
    		Client c = new Client();
    		bq.add(c);
    		arrival = rand.nextInt(5)+2;
    		System.out.printf("Adding Client %s to the queue\n", c.cID);
    		Thread.sleep(arrival*1000);
    		if(stop)
    		{
    			System.out.printf("There are %d clients totaled.\n", Client.getTotal());
    			int remain = 0;
    			while(bq.peek() != null){
    				Client temp = bq.remove();
    				remain++;
    			}
    			System.out.printf("There are %d clients remained in queue\n",remain);
    			break;
    		}
    		}
    		catch(InterruptedException e)
    		{
    			System.out.printf("Error\n",e);
    		}	
     
    	}
     
     
     
    	public static void main(String[] args)
    	{
    		BlockingQueue<Client>bankq = new LinkedBlockingQueue<Client>();
    		banker3 bank = new banker3(bankq);
    		Thread queing = new Thread(bank);
    		queing.setPriority(2);
    		Teller t1 = new Teller(bankq,1);
    		Teller t2 = new Teller(bankq,2);
    		Teller t3 = new Teller(bankq,3);
    		Teller t4 = new Teller(bankq,4);
    		Teller t5 = new Teller(bankq,5);
    		Thread tt1 = new Thread(t1);
    		tt1.setPriority(2);
    		Thread tt2 = new Thread(t2);
    		tt2.setPriority(2);
    		Thread tt3 = new Thread(t3);
    		tt3.setPriority(2);
    		Thread tt4 = new Thread(t4);
    		tt4.setPriority(2);
    		Thread tt5 = new Thread(t5);
    		tt5.setPriority(2);
    		StopWatch s = new StopWatch();
    		s.start();//start the timer
    		queing.start();
    		tt1.start();
    		tt2.start();
    		tt3.start();
    		tt4.start();
    		tt5.start();
    		while(s.isRunning())
    		{
    			if(s.elapSec() >= 120)
    			{
    				s.stop();
    				banker3.stop = true;
    				Teller.stop = true;
    				//System.out.printf("There are %d total clients\n", Client.getTotal());
    			}
     
    		}
     
     
    	}
     
     
     
    }
    //Client class
    class Client{
    private static int total = 0;
    public int waitTime;
    int cID;
    int allocatedTo;
    private static Random rand = new Random();
    public Client()
    {
    	waitTime = rand.nextInt(4)+2;
    	cID = ++total;
    	allocatedTo = rand.nextInt(6);
    }
    public static int getTotal()
    {
    	return total;
    }
     
     
    public static void setTotal()
    {
    	total--;
    }
    }
    //Teller class
    class Teller implements Runnable
    {
    	public BlockingQueue<Client>tq;
    	private int totaltime;
    	private int clientserved;
    	public static boolean stop = false;
    	public static boolean avail;
    	private static int tot = 0;
    	public static int servetime =0;
    	int tID;
    	public Teller(BlockingQueue<Client>iq, int id)
    	{
    		tq = iq;
    		tID = id;
    		avail = true;
    		clientserved =0;
    		totaltime=0;
     
    	}
     
    	public void run()
    	{
     
    		while(true)
    		try
    		{
    			serve();
    			Thread.sleep(servetime);
    			if(stop)
    			{
    				System.out.printf("Teller %d served %d clients and spent a total of %d secs\n", tID,clientserved,totaltime);
    				break;
    			}
    		}
    		catch(InterruptedException e)
    		{
    			System.out.printf("%s", e);
    		}	
    	}
     
    	public void serve()
    	{
    		Client temp = tq.peek();
    		if(temp != null && temp.allocatedTo == tID)
    		{
    			Client c = tq.remove();
    			servetime = c.waitTime;
    			clientserved++;
    			totaltime +=servetime;
    			System.out.printf("Teller %d is serving client %d\n", tID, c.cID); 
    		}
     
    	}
     
    }
     
     
    //stopwatch class
    class StopWatch {
        private long startTime = 0;
        private long stopTime = 0;
        private boolean running = false;
     
     
        public void start() {
            startTime = System.currentTimeMillis();
            running = true;
        }
     
        public void stop() {
            stopTime = System.currentTimeMillis();
            running = false;
        }
     
        //elaspsed time in milliseconds
        public long elapmili() {
            long elapsed;
            if (running) {
                 elapsed = (System.currentTimeMillis() - startTime);
            }
            else {
                elapsed = (stopTime - startTime);
            }
            return elapsed;
        }
     
    	public boolean isRunning()
    	{
    		return running;
    	}
     
        //elaspsed time in seconds
        public long elapSec() {
            long elapsed;
            if (running) {
                elapsed = ((System.currentTimeMillis() - startTime) / 1000);
            }
            else {
                elapsed = ((stopTime - startTime) / 1000);
            }
            return elapsed;
        }
     
     
    }
    Last edited by copeg; November 7th, 2010 at 02:49 PM.


  2. #2
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    Default Re: working with multiple threads

    Could be you're calling stop too early or something.

  3. #3
    Administrator copeg's Avatar
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    Default Re: working with multiple threads

    Is a LinkedBlockingQueue syncrhonized? If not, you need to synchronize calls to the object so it isn't accessed concurrently.

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