// ITI 1120 Fall 2006, Lab 8, Exercise 1
// Name: Diana Inkpen, Student# 123456

/**
 * A recursive algorithm to test if all the characters in positions 0...N of an
 * array, S of characters are digits.
 */

class CheckDigits 
{
    public static void main (String[] args)
    { 
        // DECLARE VARIABLES/DATA DICTIONARY

        char[] a;           // an array of characters
        int n;              // a position in the array.
        boolean result;     // true if positions 0 to n
                            // contain digit characters 

        // PRINT OUT IDENTIFICATION INFORMATION

        System.out.println();
        System.out.println("ITI1120 Fall 2006, Lab 8, Exercise 1");
        System.out.println("Name: Diana Inkpen, Student# 123456");

        System.out.println();

        // READ IN GIVENS

        System.out.println("Please enter characters, all in one line (no spaces): ");
        a = ITI1120.readCharLine();
        n = a.length;

        // BODY OF ALGORITHM

        result = checkDigits(a, n);      

        // PRINT OUT RESULTS AND MODIFIEDS
        System.out.println("Only digits " + result);
    }

    // If the 'main' method calls other algorithms, put the method(s) below.

    /**
     * METHOD checkDigits
     *
     * This recursive method checks to see if all characters in a character array
     * are digit characters.
     *
     * GIVENS:  arr -- a reference to an array of characters
     *          n -- the "length" of the array (it is really only the
     *               range of the array to check)
     */
    public static boolean checkDigits( char[] arr, int n )
    {
        // DECLARE VARIABLES/DATA DICTIONARY 

        boolean allDigits;  // RESULT:  True if all characters in a are
                            //          digit characters.

        // BODY OF ALGORITHM
       if(n==0)
       {
         allDigits = true;
       }
       else
       {
          if( arr[n-1] >= '0' && arr[n-1] <= '9' )
          {
             allDigits = checkDigits( arr, n-1 );;
          }
          else
          {
                allDigits = false;
          }
       }

        // RETURN RESULT

        return allDigits;
    }

}