code: public static String firstCharToLowerCase(final String source) {
  
      if (isBlank(source) || Character.isLowerCase(source.charAt(0))) {
        return source;
      }
      StringBuilder destination = getStringBuild();
      destination.append(source.substring(0, 1).toLowerCase());
      destination.append(source.substring(1));
      return destination.toString();
    }
docs: Convert first character in given string to lower case.<br>
  If given source string is blank or first character is lower case, return
  it's self.
  
  @param source string want to be handle.
  @return a new string has been converted or it's self.