src/main/java/org/jinstagram/utils/Preconditions.java
public static void checkValidRadius(String radiusString, String errorMsg) {
		checkEmptyString(radiusString, errorMsg);
		check(isNumeric(radiusString), errorMsg);
	}
public static void checkValidRadius(String radiusString, String errorMsg) {
		checkEmptyString(radiusString, errorMsg);
		check(isNumeric(radiusString), errorMsg);
	}
Check that a string is a valid radius value ('radius')
as shown in <a href="http://instagram.com/developer/realtime/">Instagram Developer real time section</a>

@param radiusString any string that is supposed to be a radius
@param errorMsg error message