Regex to match the IP Address

Yogen Rai

This has been one of the popular programming tasks for Java developer, particularly focusing on text processing. 

IPv4 addresses may be represented in any notation expressing a 32-bit integer value. They are most often written in the dot-decimal notation, which consists of four octets of the address expressed individually in decimal numbers and separated by periods.

For example, the quad-dotted IP address 172.16.255.1. 

IP example

Here is a program to match Internet Protocol version 4 (IPv4) address:

  

public class IpAddressMatcher {
    private static String pattern= "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
            "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
            "([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\." +
            "([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";

    private final Pattern regexPattern = Pattern.compile(pattern);
    
    public boolean isValidIp(final String ip) {
        Matcher matcher = regexPattern.matcher(ip);
        return matcher.matches();
    }

    @Test
    public void testIsValidIp() {
        assertTrue(isValidIp("000.12.12.034"));
        assertTrue(isValidIp("121.234.12.21"));
        assertTrue(isValidIp("23.45.12.65"));
        assertTrue(isValidIp("0.1.2.3"));
        assertFalse(isValidIp("666.666.23.23"));
        assertFalse(isValidIp(".12.32.232.23"));
    }
}

 

All source code is available on GitHub. Cheers!!