Validating IPv4 string in Java

Bellow method is validating if string is correct IPv4 address it returns true if it is valid. Any improvements in regex and elegance would be very appreciated:

public static boolean validIP(String ip) {
    if (ip == null || ip.isEmpty()) return false;
    ip = ip.trim();
    if ((ip.length() < 6) & (ip.length() > 15)) return false;

    try {
        Pattern pattern = Pattern.compile("^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$");
        Matcher matcher = pattern.matcher(ip);
        return matcher.matches();
    } catch (PatternSyntaxException ex) {
        return false;
    }
}

Solution 1:

Here is an easier-to-read, slightly less efficient, way you could go about it.

public static boolean validIP (String ip) {
    try {
        if ( ip == null || ip.isEmpty() ) {
            return false;
        }

        String[] parts = ip.split( "\\." );
        if ( parts.length != 4 ) {
            return false;
        }

        for ( String s : parts ) {
            int i = Integer.parseInt( s );
            if ( (i < 0) || (i > 255) ) {
                return false;
            }
        }
        if ( ip.endsWith(".") ) {
            return false;
        }

        return true;
    } catch (NumberFormatException nfe) {
        return false;
    }
}

Solution 2:

UPDATE: Commons-HttpClient and its successor HttpComponents-HttpClient have adopted this functionality. You can utilize this version of it like so: InetAddressUtils.isIPv4Address(Str).

The development version of Apache Commons Validator has a InetAddressValidator class which has a isValidInet4Address(String) method to perform a check to see that an given String is a valid IPv4 address.

The source code can be viewed from the repository, so that might provide some ideas for improvements, if you feel there are any.

A quick glance at the provided code shows that your method is compiling a Pattern on each invocation of the method. I would move that Pattern class out to a static field to avoid the costly pattern compilation process on each call.