Serializable, Comparable<UUID>
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_hi
The 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 UUIDs, see RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace, section 4.2 "Algorithms for Creating a Time-Based UUID".
Constructors
UUID(long mostSigBits, long leastSigBits)
Constructs a new UUID using the specified data.
int
The clock sequence value associated with this UUID.
int
Compares this UUID with the specified UUID.
boolean
Compares this object to the specified object.
Creates a
UUID
from the string standard representation as described in the
toString()
method.
long
Returns the least significant 64 bits of this UUID's 128 bit value.
long
Returns the most significant 64 bits of this UUID's 128 bit value.
int
Returns a hash code for this UUID.
Static factory to retrieve a type 3 (name based) UUID based on the specified byte array.
long
The node value associated with this UUID.
Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
long
The timestamp value associated with this UUID.
Returns a String object representing this UUID.
int
The variant number associated with this UUID.
int
The version number associated with this UUID.
public UUID(long mostSigBits, long leastSigBits)
Constructs a new UUID using the specified data. mostSigBits is used for the most significant 64 bits of the UUID and leastSigBits becomes the least significant 64 bits of the UUID.
mostSigBits - The most significant bits of the UUID
leastSigBits - The least significant bits of the UUID
()
Static factory to retrieve a type 4 (pseudo randomly generated) UUID. The UUID is generated using a cryptographically strong pseudo random number generator.
UUID
Static factory to retrieve a type 3 (name based) UUID based on the specified byte array.
name - A byte array to be used to construct a UUID
UUID generated from the specified array
Creates a
UUID
from the string standard representation as described in the
toString()
method.
name - A string that specifies a UUID
UUID with the specified value
IllegalArgumentException - If name does not conform to the string representation as described in toString()
public long getLeastSignificantBits()
Returns the least significant 64 bits of this UUID's 128 bit value.
public long getMostSignificantBits()
Returns the most significant 64 bits of this UUID's 128 bit value.
public int version()
The version number associated with this
UUID
. The version number describes how this
UUID
was generated. The version number has the following meaning:
UUID
public int variant()
The variant number associated with this
UUID
. The variant number describes the layout of the
UUID
. The variant number has the following meaning:
UUID
public long timestamp()
The timestamp value associated with this UUID.
The 60 bit timestamp value is constructed from the time_low, time_mid, and time_hi fields of this UUID. The resulting timestamp is measured in 100-nanosecond units since midnight, October 15, 1582 UTC.
The timestamp value is only meaningful in a time-based UUID, which has version type 1. If this UUID is not a time-based UUID then this method throws UnsupportedOperationException.
UUID.
UnsupportedOperationException - If this UUID is not a version 1 UUID
public int clockSequence()
The clock sequence value associated with this UUID.
The 14 bit clock sequence value is constructed from the clock sequence field of this UUID. The clock sequence field is used to guarantee temporal uniqueness in a time-based UUID.
The clockSequence value is only meaningful in a time-based UUID, which has version type 1. If this UUID is not a time-based UUID then this method throws UnsupportedOperationException.
UUID
UnsupportedOperationException - If this UUID is not a version 1 UUID
public long node()
The node value associated with this UUID.
The 48 bit node value is constructed from the node field of this UUID. This field is intended to hold the IEEE 802 address of the machine that generated this UUID to guarantee spatial uniqueness.
The node value is only meaningful in a time-based UUID, which has version type 1. If this UUID is not a time-based UUID then this method throws UnsupportedOperationException.
UUID
UnsupportedOperationException - If this UUID is not a version 1 UUID
Returns a
String
object representing this
UUID
.
The UUID string representation is as described by this BNF:
UUID = <time_low> "-" <time_mid> "-" <time_high_and_version> "-" <variant_and_sequence> "-" <node> time_low = 4*<hexOctet> time_mid = 2*<hexOctet> time_high_and_version = 2*<hexOctet> variant_and_sequence = 2*<hexOctet> node = 6*<hexOctet> hexOctet = <hexDigit><hexDigit> hexDigit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "a" | "b" | "c" | "d" | "e" | "f" | "A" | "B" | "C" | "D" | "E" | "F"
public int hashCode()
Returns a hash code for this UUID.
Compares this object to the specified object. The result is true if and only if the argument is not null, is a UUID object, has the same variant, and contains the same value, bit for bit, as this UUID.
The first of two UUIDs is greater than the second if the most significant field in which the UUIDs differ is greater for the first UUID.
compareTo in interface Comparable<UUID>
val - UUID to which this UUID is to be compared
UUID is less than, equal to, or greater than val
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