String value = _value;  int len = value.length();
int len = _chars.length;
  public boolean isLong()  {    String value = _value;        int len = value.length();    if (len == 0)      return false;        for (int i = 0; i < len; i++) {      char ch = value.charAt(i);            if (! ('0' <= ch && ch <= '9'))	return false;    }        return true;  }