Method to parse IP addresses on format x.x.x.x. Useful for sockets etc.

parseIpAddress.java

public static boolean parseIpAddress(String ip) throws IllegalArgumentException {	// IPv4, format x.x.x.x
	StringTokenizer tok = new StringTokenizer(ip, ".");

	if (tok.countTokens() != 4) {
		throw new IllegalArgumentException("IP address must be in the format 'xxx.xxx.xxx.xxx'");
	}

	int i = 0;
	while (tok.hasMoreTokens()) {
		String strVal = tok.nextToken();
		try {
			int val = Integer.parseInt(strVal, 10);

			if (val < 0 || val > 255) {
				throw new IllegalArgumentException("Illegal value '" + val + "' at byte " + (i + 1) + " in the IP address.");
			}

		} catch (NumberFormatException e) {
			throw new IllegalArgumentException("Illegal value '" + strVal + "' at token " + (i + 1) + " in the IP address.", e);
		}
	}
	
	return true;	// reach here only if no exception occurred
}