public static int countOccurrencesOf(String str, String sub) {
		if (str == null || sub == null || str.length() == 0 || sub.length() == 0) {
			return 0;
		}
		int count = 0;
		int pos = 0;
		int idx;
		while ((idx = str.indexOf(sub, pos)) != -1) {
			++count;
			pos = idx + sub.length();
		}
		return count;
	}