UUID JDK 1.6)

Description

publicfinal class UUID

A class that represents an immutable universally unique identifier (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".

See also:

Methods

Hide/Show inherited methods

public int clockSequence ()

The clock sequence value associated with this UUID.

public int compareTo (UUID val)

Compares this UUID with the specified UUID.

public boolean equals (Object obj)

Compares this object to the specified object.

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.
Returns: true if the objects are the same; false otherwise.
Parameters:
- obj - the object to compare with.

publicstatic UUID fromString (String name)

Creates a UUID from the string standard representation as described in the UUID.toString() method.

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 hashCode ()

Returns a hash code for this UUID.

Returns a hash code for this UUID.
Returns: a hash code value for this UUID.

publicstatic UUID nameUUIDFromBytes (byte[] name)

Static factory to retrieve a type 3 (name based) UUID based on the specified byte array.

public long node ()

The node value associated with this UUID.

publicstatic UUID randomUUID ()

Static factory to retrieve a type 4 (pseudo randomly generated) UUID.

Static factory to retrieve a type 4 (pseudo randomly generated) UUID.

The UUID is generated using a cryptographically strong
pseudo random number generator.
Returns: a randomly generated UUID.

public long timestamp ()

The timestamp value associated with this UUID.

public String toString ()

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"

Returns: a string representation of this UUID.

public int variant ()

The variant number associated with this UUID.

public int version ()

The version number associated with this UUID.