Need help assigning range for an integer for subtracting time.

Question

Ok, so I'm having a little trouble getting this program to work. :x Maybe somebody could give me some help on what to do next. I'm new to Java, and I'm trying to write a program using NetBeans 6.9.1, and I ran into a problem. I'm trying to write a program for a time traveler Marty, who is going back in time. The time is set on a 24 hour clock, so am and pm is not an issue.
I have the program written, but I'm having trouble with the subtraction of the time. Whenever I do the subtract, and the time traveled back (either in hours, minutes or seconds), is bigger than the current time, I just end up with negative numbers. I don't know how to set the value so it will just recycle through the 24 hours, the 60 minutes, or 60 seconds, instead of giving me negative numbers. Any help would be greatly appreciated. Also, I'm not sure how to make the users input italic. Here is what I got so far.
package timetravel;
* @author Jeff
import java.io.*;
import java.util.*;
public class Main {
* @param args the command line arguments
public static void main(String[] args) {
int hours, minutes, seconds, hoursback, minutesback, secondsback;
Scanner keyboard = new Scanner (System.in);
System.out.println("Hi Marty!");
System.out.println("Enter current hour:");
hours = keyboard.nextInt();
System.out.println("Enter current minute:");
minutes = keyboard.nextInt();
System.out.println("Enter current second:");
seconds = keyboard.nextInt();
System.out.println("Enter how many hours you want to travel back");
hoursback = keyboard.nextInt();
System.out.println("Enter how many minutes you want to travel back");
minutesback = keyboard.nextInt();
System.out.println("Enter how many seconds you want to travel back");
secondsback = keyboard.nextInt();
System.out.println("When you arrive, the local time will be " + (hours - hoursback)
+ " hours, " + (minutes - minutesback) + " minutes, and " + (seconds - secondsback)
+ " seconds.");

Answer 1

Well, basically, here's how I want the program to run
Example program run:
Hi Marty!
Enter current hour: 8
Enter current minute: 12
Enter current second: 11
Enter how many hours you want to travel back: 9
Enter how many minutes you want to travel back: 36
Enter how many seconds you want to travel back: 39
When you arrive, the local time will be: 22 hours, 35 minutes, and 32 seconds
(program input is written in italic)
instead of how it runs now
Hi Marty!
Enter current hour: 8
Enter current minute: 12
Enter current second: 11
Enter how many hours you want to travel back: 9
Enter how many minutes you want to travel back: 36
Enter how many seconds you want to travel back: 39
When you arrive, the local time will be: -1 hours, -24 minutes, and -28 seconds
I want it to cycle through the 24 hour clock, so if I travel back in time from 18 (1800 or 6pm) and i want to travel back in time 20 hours, I should get 22 (2200 or 10 pm) instead of -2.
Same with minutes and seconds, except for it to cycle through 60 instead of 24, since there are 60 minutes in an hour, and 60 seconds in a minute. Also, if the minutes end up being negative, I need it to take away one from the hour spot, and so on for the other ones. Hopefully I explained it well enough... Sorry, I'm new to Java.
Edited by: halo2jak on Sep 7, 2010 12:24 AM