code: public static int indexOneOf(CharSequence string, char... chars)
    {
      for(int i = 0; i < string.length(); ++i) {
        for(int j = 0; j < chars.length; ++j) {
          if(string.charAt(i) == chars[j]) {
            return i;
          }
        }
      }
      return -1;
    }
docs: Search string index of the first character from a series. Traverse <code>string</code> and compare with character
  from <code>chars</code> series one by one, in sequence. If found return string index; if reach the end of the
  string return -1.
  
  @param string string builder to search on,
  @param chars characters series.
  @return index of first character from series or -1.