jodd-core/src/main/java/jodd/io/NetUtil.java
public static boolean validateAgaintIPAdressV4Format(final String input) {
		if (input == null) {
			return false;
		}

		int hitDots = 0;
		char[] data = input.toCharArray();
		for (int i = 0; i < data.length; i++) {
			char c = data[i];
			int b = 0;
			do {
				if (c < '0' || c > '9') {
					return false;
				}
				b = (b * 10 + c) - 48;
				if (++i >= data.length) {
					break;
				}
				c = data[i];
			} while (c != '.');

			if (b > 255) {
				return false;
			}
			hitDots++;
		}

		return hitDots == 4;
	}
public static boolean validateAgaintIPAdressV4Format(final String input) {
		if (input == null) {
			return false;
		}

		int hitDots = 0;
		char[] data = input.toCharArray();
		for (int i = 0; i < data.length; i++) {
			char c = data[i];
			int b = 0;
			do {
				if (c < '0' || c > '9') {
					return false;
				}
				b = (b * 10 + c) - 48;
				if (++i >= data.length) {
					break;
				}
				c = data[i];
			} while (c != '.');

			if (b > 255) {
				return false;
			}
			hitDots++;
		}

		return hitDots == 4;
	}
Checks given string against IP address v4 format.

@param input an ip address - may be null
@return <tt>true</tt> if param has a valid ip v4 format <tt>false</tt> otherwise
@see <a href="https://en.wikipedia.org/wiki/IP_address#IPv4_addresses">ip address v4</a>