Adding arrays - confusing question

Question

I am in the process of writing a java program where I have to add arrays. The question asks:
This program asks you to assume that your computer has the very limited capability of being able to read and write only single-digit integers and to add together two integers consisting of one decimal digit each. Write a program that can read in two integers of up to 40 digits each, add these digits together, and display the result. Test your program using pairs of numbers of varying lengths. You must use arrays in this problem.
I think I understand up to there is says"Write a program that can read in two integers of up to 40 digits each" from there I am lost.
Can anyone help explain what is needed?
This is what i have so far:
import java.util.*;
public class add
    public static void main(String[] args)
      Scanner in = new Scanner(System.in);
      int x = in.nextInt();
      int y = in.nextInt();
        int[] a = {x};
        int[] b = {y};
        int[] ab = new int[a.length + b.length];
        System.arraycopy(a, 0, ab, 0, a.length);
        System.arraycopy(b, 0, ab, a.length, b.length);
        System.out.println(Arrays.toString(ab));
}

Answer 1

Yeh, sorry about that didn't have the time to go ahead and drag some of the code over when I first found this forum, first thing I tried a quick compile and run just to see what problems I'd get and I got this runtime error of: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 7
     at java.lang.String.charAt(String.java:687)
     at Joseph_Ryan_P2.main(Joseph_Ryan_P2.java:36)
I threw in some print statements to see how far it gets before the error occurs and it seems to be right before the for loop(see code below)
In this program I'm reading in from a text file that will read two numbers from the same line that are seperated by a space and eventually add them, is the best way to do that by using a tokenizer or some sort of space delimiter? Or is there an easier way? If the tokenizer is best how would i go about that I haven't learned too much about them besides the fact that they exist so far.
Thanks for any help you or suggestions you guys can give.
//Joseph_Ryan_P2.java
//Big Integer Program
//Description:
//     Design and implement a BigInteger class that can add and subtract integers with up to 25 digits. Your
//     class should also include methods for input and output of the numbers.
// Must Use Arrays
import java.io.*;               //neccessary imported libraries
import java.util.*;
public class Joseph_Ryan_P2          
     public static void main(String[] args)          //the programs main method
          try
               Scanner scan = new Scanner(new File("BigInts")); //Scanner to read in from plaintext file
          String numline = scan.next();
          int x=0;
          int [] big1 = new int [numline.length()];
          System.out.println(numline);
               int [] big2 = new int [numline2.length()];
               String numline2= scan.nextLine();
               System.out.println(numline2);
          for(int i = numline.length() - 1; i >= 0; i++)
          char current = numline.charAt(i);
          int d = (int) current - (int) '0';
               big1[i] = d;
          }//end for loop
          }//end try
          catch(FileNotFoundException exception)
System.out.println("The file could not be found.");
catch(IOException exception)
System.out.println(exception);
} //end catch statements
     }//end main
}//end class