public static String extractDigits(String s) {
		if (s == null) {
			return StringPool.BLANK;
		}

		StringBuilder sb = new StringBuilder();

		char[] chars = s.toCharArray();

		for (char c : chars) {
			if (Validator.isDigit(c)) {
				sb.append(c);
			}
		}

		return sb.toString();
	}