Review

class Hex {
   /**
    * Interprets the character <code>c</code> as hexadecimal digit.
    *
    * @param c a character from '0', '1', '2', '3', '4', '5', '6', '7', '8',
    *    '9', 'A', 'B', 'C', 'D', 'E', 'F'.
    *
    * @return the decimal-hexadecimal digit interpretation of
    *    <code>c</code>.
    */
   static int hexDigitToInt(char c)
   throws NumberFormatException {
      switch (c) {
         case '0': return 0;
         case '1': return 1;
         case '2': return 2;
         case '3': return 3;
         case '4': return 4;
         case '5': return 5;
         case '6': return 6;
         case '7': return 7;
         case '8': return 8;
         case '9': return 9;
         case 'a': case 'A': return 10;
         case 'b': case 'B': return 11;
         case 'c': case 'C': return 12;
         case 'd': case 'D': return 13;
         case 'e': case 'E': return 14;
         case 'f': case 'F': return 15;
         default: throw new NumberFormatException();
      }
   }

}