Validate UUID

In this article, we will take a look at 2 different ways to validate a UUID string in java with examples.

What is UUID ?

UUID stands for Universal Unique IDentifier.
A UUID is a unique identifier that is used to identify a device or a piece of data. UUIDs are typically generated by a device or a service, and are then used to identify that device or service.

UUID has a fixed format having 5 blocks where each block has a fixed length of digits as below

Name	Length(Hex digits)
time_low	8
time_mid	4
time_high_and_version	4
variant_and_sequence	4
node	12

Remember that UUID comprises of alphanumeric characters.

Reasons to validate

There are a couple of reasons to validate a UUID string in Java.
1. To make sure that a UUID string that is being passed to your Java application is in the correct format.
2. To validate a UUID string to make sure that it is not being used to spoof a device or service.

Validate UUID string in Java

There are 2 ways to validate a UUID string in Java.

1. Using java.util.UUID

This class has a static method fromString() that takes a string argument returns an object of java.util.UUID.
If the string is not in the correct format, then this method will throw an IllegalArgumentException. Example,

UUID valid = UUID.fromString("30de749c-10b8-4be0-a077-5eb486197a29");
System.out.println(valid);
UUID invalid= UUID.fromString("AF");
System.out.println(invalid);

Output is

2. Using regex

Another way to validate a UUID string is to use a regular expression.
A regular expression is a pattern that can be used to match a string. There are a few different regular expressions that can be used to match a UUID string.
One of those is

This regular expression will match a UUID string that is in the correct format.

String regex = "^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$";
Pattern pattern = Pattern.compile(regex);
System.out.println(
      pattern.matcher("c0d69b05-c468-4d28-9779-c433e7364be6").matches());
System.out.println(
      pattern.matcher("ABFCD").matches());

Output is

Conclusion

This article demonstrated 2 different ways to validate UUID string in java.
First is using UUID class in java itself.
Second is to validate the UUID string against a regular expression based on the format of standard UUID.