code: public static String convert32(String s)
      {
          try {
              byte[] bytes = s.getBytes();
              MessageDigest md = MessageDigest.getInstance("MD5");
              md.update(bytes);
              bytes = md.digest();
              int j = bytes.length;
              char[] chars = new char[j * 2];
              int k = 0;
              for (int i = 0; i < bytes.length; i++) {
                  byte b = bytes[i];
                  chars[k++] = hexChars[b >>> 4 & 0xf];
                  chars[k++] = hexChars[b & 0xf];
              }
              return new String(chars);
          }
          catch (Exception e){
              return null;
          }
      }
docs: 32位MD5加密算法
  @param s
  @return