java.util
Class UUID
public final
class
UUID
extends Object
implements Serializable, Comparable<UUID>
This class represents a 128-bit UUID value.
There are several types of UUID, and while this class can be used to store
them, only the Leach-Salz (variant 2) UUID specified in RFC-4122 will
give meaningful results from the method calls.
See: http://tools.ietf.org/html/4122 for the details
The format of a Leach-Salz (variant 2) time-based (version 1) UUID
is as follows:
time_low - upper 32 bits of the most significant 64 bits,
this is the least-significant part of the timestamp.
time_mid - bits 16-31 of the most significant 64 bits,
this is the middle portion of the timestamp.
version - bits 8-15 of the most significant 64 bits.
time_hi - bits 0-7 of the most significant 64 bits,
the most significant portion of the timestamp.
clock_and_reserved - bits 48-63 of the least significant 64 bits.
a variable number of bits hold the variant
(see the spec)
node identifier - bits 0-47 of the least signficant 64 bits.
These fields are valid only for version 1, in the remaining versions,
only the version and variant fields are set, all others are used for data.
Since: 1.5
| Method Summary |
|---|
| int | clockSequence()
Returns the clock-sequence value of this UUID.
|
| int | compareTo(UUID o)
Compare this UUID to another.
|
| boolean | equals(Object obj)
Compare a (UUID) object to this one |
| static UUID | fromString(String name)
Creates a UUID object from a Sting representation.
|
| long | getLeastSignificantBits()
Returns the least significant 64 bits of the UUID as a long. |
| long | getMostSignificantBits()
Returns the most significant 64 bits of the UUID as a long. |
| int | hashCode()
Returns a hash of this UUID. |
| static UUID | nameUUIDFromBytes(byte[] name)
Creates a UUID version 3 object (name based with MD5 hashing)
from a series of bytes representing a name. |
| long | node()
Returns the 48-bit node value in a long.
|
| static UUID | randomUUID()
Generate a Leach-Salz (Variant 2) randomly generated (version 4)
UUID.
|
| long | timestamp()
Returns the 60-bit timestamp value of the UUID in a long.
|
| String | toString()
Returns a String representation of the UUID.
|
| int | variant()
Returns the variant of the UUID
This may be:
0 = Reserved for NCS backwards-compatibility
2 = Leach-Salz (supports the other methods in this class)
6 = Reserved for Microsoft backwards-compatibility
7 = (reserved for future use) |
| int | version()
Returns the version # of the UUID.
|
public UUID(long mostSigBits, long leastSigBits)
Constructs a new UUID.
Since: 1.5
public int clockSequence()
Returns the clock-sequence value of this UUID.
This field only exists in a time-based (version 1) UUID.
Throws: UnsupportedOperationException if the UUID type is not 1.
UNKNOWN: an int containing the clock-sequence value.
public int compareTo(
UUID o)
Compare this UUID to another.
The comparison is performed as between two 128-bit integers.
Returns: -1 if this < val, 0 if they are equal, 1 if this > val.
public boolean equals(
Object obj)
Compare a (UUID) object to this one
Creates a UUID object from a Sting representation.
For the format of the string,
Returns: a new UUID object.
See Also:
public long getLeastSignificantBits()
Returns the least significant 64 bits of the UUID as a long.
public long getMostSignificantBits()
Returns the most significant 64 bits of the UUID as a long.
public int hashCode()
Returns a hash of this UUID.
public static
UUID nameUUIDFromBytes(byte[] name)
Creates a UUID version 3 object (name based with MD5 hashing)
from a series of bytes representing a name.
public long node()
Returns the 48-bit node value in a long.
This field only exists in a time-based (version 1) UUID.
Throws: UnsupportedOperationException if the UUID type is not 1.
UNKNOWN: a long with the node value in the lower 48 bits.
public static
UUID randomUUID()
Generate a Leach-Salz (Variant 2) randomly generated (version 4)
UUID.
public long timestamp()
Returns the 60-bit timestamp value of the UUID in a long.
This field only exists in a time-based (version 1) UUID.
Throws: UnsupportedOperationException if the UUID type is not 1.
UNKNOWN: a long with the timestamp value.
Returns a String representation of the UUID.
The format of the standard string representation (given in RFC4122) is:
time-low "-" time-mid "-"
time-high-and-version "-"
clock-seq-and-reserved
clock-seq-low "-" node
Where each field is represented as a hex string.
Returns: the String representation.
public int variant()
Returns the variant of the UUID
This may be:
0 = Reserved for NCS backwards-compatibility
2 = Leach-Salz (supports the other methods in this class)
6 = Reserved for Microsoft backwards-compatibility
7 = (reserved for future use)
public int version()
Returns the version # of the UUID.
Valid version numbers for a variant 2 UUID are:
1 = Time based UUID
2 = DCE security UUID
3 = Name-based UUID using MD5 hashing
4 = Randomly generated UUID
5 = Name-based UUID using SHA-1 hashing
Returns: the version number