public static boolean is_integer(String str) {
		if (str == null) return false;
		if (str.equals("")) return false;
		Character c = str.charAt(0);
		if (!c.equals('-') && !c.equals("+") && !Character.isDigit(c)) return false;
		try {
			@SuppressWarnings("unused")
			Integer test = parseInt(str);
		} catch (NumberFormatException e) {
			return false;
		}
		return true;
	}