java.lang.Object java.util.UUID
A class that represents a 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 UUIDs, see the expired Internet-Draft UUIDs and GUIDs or the standards body definition at ISO/IEC 11578:1996.
Constructor Summary | |
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UUID(DataInput in)
Constructs a new UUID using 16 bytes read from the specified data source in standard network byte order. |
|
UUID(long mostSigBits,
long leastSigBits)
Constructs a new UUID using the specified data. |
Method Summary | |
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int |
clockSequence()
The clock sequence value associated with this UUID. |
int |
compareTo(UUID val)
Compares this UUID with the specified UUID. |
boolean |
equals(Object obj)
Compares this object to the specified object. |
static UUID |
fromString(String name)
Creates a UUID from the string standard representation as described in the toString() method. |
int |
hashCode()
Returns a hash code for this UUID . |
static UUID |
nameUUIDFromBytes(byte[] name)
Static factory to retrieve a type 3 (name based) UUID based on the specified byte array. |
static UUID |
nameUUIDFromString(String name)
Static factory to retrieve a type 3 (name based) UUID based on the specified String. |
long |
node()
The node value associated with this UUID. |
static UUID |
randomUUID()
Static factory to retrieve a type 4 (pseudo randomly generated) UUID. |
long |
timestamp()
The timestamp value associated with this UUID. |
String |
toString()
Returns a String object representing this
UUID . |
int |
variant()
The variant number associated with this UUID. |
int |
version()
The version number associated with this UUID. |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Methods inherited from interface java.lang.Comparable |
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compareTo |
Constructor Detail |
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public UUID(long mostSigBits, long leastSigBits)
mostSig
- leastSig
- public UUID(DataInput in) throws IOException
in
- - the input stream to read data from
IOException
- - if an error occurs while reading 16 bytesMethod Detail |
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public static UUID randomUUID()
public static UUID nameUUIDFromString(String name)
a
- string to be used to construct a UUID.
public static UUID nameUUIDFromBytes(byte[] name)
a
- byte array to be used to construct a UUID.
public static UUID fromString(String name)
a
- string that specifies a specific UUID.
public int version()
public int variant()
public long timestamp()
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.
UnsupportedOperationException
- if this UUID is not a
version 1 UUID.public int clockSequence()
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.
UnsupportedOperationException
- if this UUID is not a
version 1 UUID.public long node()
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.
UnsupportedOperationException
- if this UUID is not a
version 1 UUID.public String toString()
String
object representing this
UUID
.
The UUID string representation is as described by this BNF :
UUID ="-" "-" "-" "-" time_low = 4* time_mid = 2* time_high_and_version = 2* variant_and_sequence = 2* node = 6* hexOctet = hexDigit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "a" | "b" | "c" | "d" | "e" | "f" | "A" | "B" | "C" | "D" | "E" | "F"
toString
in class Object
public int hashCode()
UUID
.
hashCode
in class Object
Object.equals(java.lang.Object)
,
Hashtable
public boolean equals(Object obj)
equals
in class Object
obj
- the object to compare with.
true
if the objects are the same;
false
otherwise.Object.hashCode()
,
Hashtable
public int compareTo(UUID val)
The first of two UUIDs follows the second if the most significant field in which the UUIDs differ is greater for the first UUID.
An IllegalArgumentException is thrown if the argument is not of the same variant type as this UUID.
val
- UUID to which this UUID is to be compared.
IllegalArgumentException
- if val is a different
variant of UUID.