Thread: Queue Simulation

Hi im trying to simulate a waiting queue by using Java. What my program must consist of:

• The user input nth number of cashiers

• There minimum of 10 customers will arrive in the queue in random intervals.

• When a cashier is free the the next customer is line will be processed.

• The program must output each stage of the queue as well as the time each customer spent in the queue.

• Oki so what I have so is a empty queue object, a random string list generator which sends the strings to the queue.

However what problems im having is the random string generator is picking duplicates in the loop, how do I fix this ? Also how do I make it send the customers to the queue in intervals of 0.5 sec and I need to record the time they enter the queue and leave the queue so then I can output the time spent in the queue. Im stuck dont know what to do now ?

public static Queue<String> line = new  LinkedList<String> ();
 
public static void main(String[] args) 
{
    String[] list = {"a", "b", "c", "e", "f", "g", "h", "i", "j", "k", };
    int customer = list.length;
 
    for (int x = 0; x < customer; x++ )
    {
      int cus = (int) (Math.random() * customer);
      line.add(list[cus]);
    }
}

Yep really stuck on this

Honestly the instructor has just taught us about loops, Recursion and we haven't even done random generators yet but ive done it for my self.

I believe the whole thing can run faster like you said 30ms

Oki I understand that but what recording the time you have to record the time the customer went in the queue and then went out the queue to able to know the time spent in the queue. Is it possible to process this in the cashier ?

Can you start me off with the coding.

Just accumulate values you allocate and call them the time spent? Why do you need a clock if you know what the time intervals are?

Starstreak can you explain abit more how would that me done.

remember the user will input how many cashiers exist. To know of the cashier is free cant the been done with a if statement in thread. Also how did u work out the random time vales of 60 - 160 sec.

remember the user will input how many cashiers exist. To know of the cashier is free cant the been done with a if statement in thread. Also how did u work out the random time vales if 60 - 160 sec.

can u start me of with threads coding plz

oki ill read up about it and start testing ill get back to when I have a problem lol

Ive read up on threads and so far Ive managed to get loop working with outputting the customer name and the time they were served by using methods in another class. However Im still stuck on if the user inputs nth number of cashier which basically mean the whole loop will run x(nth cashier inputted).

while (!line.isEmpty())
		{
			System.out.println(line  + "\n");
			System.out.println("The queue has " + line.size() + " customers left");
			Customer cus = line.remove();
			System.out.println(cus.name + " queued at " + cus.getTime() + " <=== SERVED" + "\n");
			// you will have to sleep a random number of seconds here
			int wait = ran.nextInt(2) + 1;  // will generate 1 or 2
			try 
			{
			     Thread.sleep(wait * 1000);
			}
			catch(Exception e) 
			{
				System.out.println("Sleep error: " + e);
			}

Originally Posted by spiderd

Starstreak can you explain abit more how would that me done.

Well, Norm seems to advocate a real time simulation, whereas I propose just calculating and accumulating known (random) time intervals. You then pump them out in one go during runtime.

For the actual queue, how about a Java List, where data can be appended (FIFO)?

{Throwing ideas about here )

The instructor hasn't specifed whether real time or event time is there any existing examples you can refer me to so i can get a better understanding and get some practice.