code: public static String decodeUnicodeString(String s) {
      if (Strings.isNullOrEmpty(s)) return s;
  
      int length = s.length();
      StringBuilder sb = new StringBuilder(length);
      Matcher m = UNICODE_PATTERN.matcher(s);
      int begin = 0;
      while (m.find()) {
        int start = m.start();
        if (start > 0 && s.charAt(start - 1) == '\u0003') {
          if (start - 1 > begin) {
            sb.append(s, begin, start - 1);
          }
          begin = start;
          continue;
        }
        sb.append(s, begin, start);
        String mcStr = m.group(1);
        try {
          char charValue = (char) Integer.parseInt(mcStr, 16);
          sb.append(charValue);
          begin = m.end();
        } catch (NumberFormatException e) {
          System.out.println(e.getMessage());
        }
      }
  
      if (begin < length) {
        sb.append(s, begin, length);
      }
      return sb.toString();
    }
docs: 转换\\u123这种编码为正常字符
  
  @param s 待转换字符
  @return String