code: public static String charToEscape(char ch) {
          String hexValue = Integer.toHexString(ch);
          if (hexValue.length() == 1) {
              return "\\u000" + hexValue;
          }
          if (hexValue.length() == 2) {
              return "\\u00" + hexValue;
          }
          if (hexValue.length() == 3) {
              return "\\u0" + hexValue;
          }
          return "\\u" + hexValue;
      }
docs: Return the Java Unicode escape sequence for the given character. For example, the
  null character (0x00) is converted to the string "\u0000". This method is useful
  for creating display-friendly strings that contain hidden non-printable characters.
  
  @param ch    Character to be converted.
  @return      String containing the Java Unicode escape sequence for the given
  character.