public static int
intValue(String option) {
	String s = value(option);
	if (s != null) {
		try {
			int val = Integer.parseInt(s);
			if (val > 0)
				return (val);
		}
		catch (NumberFormatException e) {
		}
	}
	return (-1);
}
Returns the value of an option as an integer, or -1 if not defined.
src/main/java/core/org/xbill/DNS/Options.java