docs: private static String upperCaseHex(String s) {
          char chars[] = s.toCharArray();
          int length = s.length();
  
          for (int i = 0; i < length; i++) {
  
              switch (chars[i]) {
                  case 'a':
                      chars[i] = 'A';
                      break;
                  case 'b':
                      chars[i] = 'B';
                      break;
                  case 'c':
                      chars[i] = 'C';
                      break;
                  case 'd':
                      chars[i] = 'D';
                      break;
                  case 'e':
                      chars[i] = 'E';
                      break;
                  case 'f':
                      chars[i] = 'F';
                      break;
              }
          }
  
          return new String(chars);
      }