The java.util.UUID class represents an immutable universally unique identifier (UUID).Following are the important points about UUID − A UUID represents a 128-bit value. It is used for for creating random file names, session id in web application, transaction id etc.

How does Java UUID work?

A UUID is made up of hex digits (4 chars each) along with 4 “-” symbols, which make its length equal to 36 characters. The Nil UUID is a special form of UUID in which all bits are set to zero. In this tutorial, we will have a look at the UUID class in Java.

Is Java UUID really unique?

While the UUIDs are not guaranteed to be unique, the probability of a duplicate is extremely low. See Random UUID probability of duplicates. For your application, it makes sense to use the UUID, but you may want to deal with the extremely rare condition, just in case.