code: static String hex0(final byte x) {
          final char tab[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                  'a', 'b', 'c', 'd', 'e', 'f' };
          int uint;
          if (x < 0) {
              uint = x & 0x7F;
              uint |= 1 << 7;
          } else {
              uint = x;
          }
          return "" + tab[uint >>> 4] + tab[uint & 0xF];
      }
docs: Used to debug print a message digest