title: adding and subtracting strings in Java
body: <p>I need some help on a program i'm supposed to create. i'm supposed to create a program that reads two strings of any length that are user inputted and it subtracts or adds them together. i'm NOT allowed to convert these strings into numbers before the operation. this is what I got so far.My teacher mentioned something like converting the strings into uni-code to add and subtract them but i have no idea how to do it as we haven't even learned uni-code. HERE IS MY CODE: </p>
  
  <pre><code>import java.util.Scanner;
  public class Number {
      private char Sign;
      private String Whole;
      private String Fraction;
  
      public static void main(String[] args) {
          Scanner Keyboard = new Scanner (System.in);
          System.out.println("This program adds or subtracts numbers of any lengths, please add two numbers: ");
          String num1 = Keyboard.nextLine();
          System.out.println("Enter the second number: ");
          String num2 = Keyboard.nextLine();
  
          String sum = " ";
          int length = num1.length();
          int carry = 0;
  
          public Number Add(Number RHS) {
  
              for (int i = length -1 ; i &gt;= 0; i--) {
                  char c1 = num1.charAt(i);
                  char c2 = num2.charAt(i);
  
                  int tempSum = (c1 - 48) + (c2 - 48) + carry;
                  carry = tempSum / 10;
  
                  int sumDigit = tempSum % 10;
                  sum = (char) (sumDigit + 48) + sum;
  
                  if (carry == 1) {
                      sum = "1" + sum;
                  }
              }
          }
      }
      public Number (double n) {
          Whole = " ";
          Fraction = " ";
          if (n &gt;= 0) {
              Sign = '+';
          }
          else 
          {
              Sign = '-';
              n = Math.abs(n);
              String numString = new Double(n).toString();
              int position = numString.indexOf(".");
          }
  
      }
  }
  </code></pre>