A class that represents an immutable universally unique identifier (UUID). A UUID represents a 128-bit value.
There exist different variants of these global identifiers. The methods of this class are for manipulating the Leach-Salz variant, although the constructors allow the creation of any variant of UUID (described below).
The layout of a variant 2 (Leach-Salz) UUID is as follows: The most significant long consists of the following unsigned fields:
The least significant long consists of the following unsigned fields:
The variant field contains a value which identifies the layout of the
UUID. The bit layout described above is valid only for a
UUID with a variant value of 2, which indicates the Leach-Salz variant.
The version field holds a value that describes the type of this
UUID . There are four different basic types of UUIDs: time-based, DCE security, name-based, and randomly generated UUIDs. These types have a version value of 1, 2, 3 and 4, respectively.
For more information including algorithms used to create
UUIDs, see RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace , section 4.2 "Algorithms for Creating a Time-Based UUID".