java question

lime · Nov 7, 2004, 05:45 PM

i'm working on a simulator project and i'm having trouble in one area....

i run a simulation of planes landing and taking off on one runway, the user inputs the minutes to run the sim, the prob of a plane landing and taking off, the minutes it takes to land and to take off....the constructor and everything is fine but i'm having trouble in this one method

the method runs the actual simulation ... it generates random doubles to check if a plane wants to land and if a plane wants to take off, if so it adds them to the appropriate queue. the part i'm having trouble with is getting the average wait time in the queue and the number of planes left in each queue....here's the code i have for this method so far, any ideas ????

Code:

public void runSim() {
 		rnd = new Random();
 		while(interval <= minutes){
 			temp = rnd.nextDouble();
 			if(temp < probLand){
 				landingQ.add(new airplane(interval));
 			}
 			temp = rnd.nextDouble();
 			if(temp < probTake){
 				takeOffQ.add(new airplane(interval));
 			}
 			if(landingQ.size() > maxLand)
 				maxLand++;
 			if(takeOffQ.size() > maxTake)
 			    maxTake++;		    
 			if(!landingQ.isEmpty()){
 				landed++;
 			    landSum += interval - ((airplane)landingQ.front()).getStart();
 				landingQ.remove();
 				interval += minToLand;
 			}
 			else if((landingQ.isEmpty()) && (!takeOffQ.isEmpty())){
 				tookOff++;
 			    takeSum += interval - ((airplane)takeOffQ.front()).getStart();
 				takeOffQ.remove();
 				interval += minToTake;
 			}
 			else if((landingQ.isEmpty()) && (takeOffQ.isEmpty())){
 				interval++;
 		    }			
 		} // end while
 		leftLand = landingQ.size();
 		leftTake = takeOffQ.size();
 		if(landed == 0)
 			avgLand = 0;
 		else
 			avgLand = landSum/landed;
 		if(tookOff == 0)
 			avgTake = 0;
 		else
 			avgTake = takeSum/tookOff;
 	} // end method runSim()

pr0digal jenius · Nov 8, 2004, 03:18 AM

i'll look at it tomorrow when I'm more awake, just thought I'd let you knwo now so you wouldn't think you'd been abandoned

pr0digal jenius · Nov 9, 2004, 04:26 PM

hrmm..I dunno...that's a really round about way to do the program.....what all is in your landingQ class?

lime · Nov 9, 2004, 05:42 PM

the landingQ is just an UnboundedQueue....it's fine...i just need help on how to check if the runway is free, if so and the landingQ isn't empty, then allow a plane to land, so the runway is not free for minToLand minutes....then go from there... i'm having trouble with that part

bug77 · Nov 9, 2004, 06:08 PM

My guess is landSum, landed, takeSum, tookOff are of an integral type. In this case, you need to convert at least one of the operands to a float.
E.g.: avgLand = (float)landSum/landed;

On the other hand, double type is a performance killer on 32 bit platforms, so you'd be better off with float. Or if that is not a concern, just use
if(Math.random()<whatever){
}

I hope that solves your problem. If not get back to me.

germanjulian · Nov 9, 2004, 06:14 PM

why dont you go to a developer forum where you will get loads more help.
devshed.com for example

not saying the people here dont know cause some of them do but on developer forums its all about develoing

bug77 · Nov 9, 2004, 09:44 PM

Quote:

Originally Posted by lime

the landingQ is just an UnboundedQueue....it's fine...i just need help on how to check if the runway is free, if so and the landingQ isn't empty, then allow a plane to land, so the runway is not free for minToLand minutes....then go from there... i'm having trouble with that part

Have a boolean value tell if the runway is free. Whenever it is in use for a period of time, set the value to indicate that and have a thread sleep for that amount of time and reset the value afterwards.

lime · Nov 10, 2004, 08:41 PM

well we had a lab exam with a similar problem and i figured out how to do that in the exam....so know my program works...i did use a boolean for runwayFree and it works better now....thanks for your help

slinkydink · Nov 21, 2004, 06:47 PM

code looks good, although I would use math.random instead