code: public static char forDigit(int digit, int radix) {
          if (digit >= 0 && digit < radix && radix >= Character.MIN_RADIX && radix <= MAX_RADIX) {
              return digits[digit];
          }
          return '\u0000';
      }
docs: Determines the character representation for a specific digit in the
  specified radix.
  
  Note: If the value of radix is not a valid radix, or the value of digit
  is not a valid digit in the specified radix, the null character
  ('\u0000') is returned.
  
  @param digit
  @param radix
  @return