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:
0xFFFFFFFF00000000 time_low 0x00000000FFFF0000 time_mid 0x000000000000F000 version 0x0000000000000FFF time_hiThe least significant long consists of the following unsigned fields:
0xC000000000000000 variant 0x3FFF000000000000 clock_seq 0x0000FFFFFFFFFFFF node
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
see RFC 4122: A
Universally Unique IDentifier (UUID) URN Namespace, section 4.2
"Algorithms for Creating a Time-Based UUID".