Last updated: February 8, 2023
In this short tutorial, we’ll see how to validate IPv4 addresses in Java.
Our valid IPv4 address is in the form “x.x.x.x”, where each x is a number in the range 0 <= x <= 255, does not have leading zeros, and is separated by a dot.
Here are some valid IPv4 addresses:
And some invalid ones:
We can use the InetAddressValidator class from the Apache Commons Validator library to validate our IPv4 or IPv6 address.
Let’s add a dependency to our pom.xml file:
<dependency>
<groupId>commons-validator</groupId>
<artifactId>commons-validator</artifactId>
<version>1.7</version>
</dependency>Then, we just need to use the isValid() method of an InetAddressValidator object:
InetAddressValidator validator = InetAddressValidator.getInstance();
validator.isValid("127.0.0.1");Alternatively, we can use the InetAddresses class from the Guava library to achieve the same goal:
InetAddresses.isInetAddress("127.0.0.1");Finally, we can also use Regex:
String regex = "^((25[0-5]|(2[0-4]|1\\d|[1-9]|)\\d)\\.?\\b){4}$";
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(ip);
matcher.matches();In this regular expression, ((25[0-5]|(2[0-4]|1\\d|[1-9]|)\\d)\\.?\\b) is a group that is repeated four times to match the four octets in an IPv4 address. The following matches each octet:
So, this regex matches IPv4 addresses.
In summary, we’ve learned different ways to validate IPv4 addresses in Java.
The example code from this article can be found over on GitHub.
