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Java uuid from bytes

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  1. Java uuid from bytes
  2. UUID
  3. UUID
  4. UUID
  5. UUID
  6. UUID
  7. UUID
  8. fromString
  9. toString
  10. toUrn
  11. equals
  12. hashCode
  13. compareTo
  14. clockSequence
  15. version
  16. variant
  17. node
  18. timestamp
  19. getRawBytes
  20. randomUUID
  21. timeUUID
  22. nameUUIDFromString
  23. nameUUIDFromString
  24. Java UUID
  25. UUID Versions and Variants:
  26. Generating a UUID:
  27. 1. randomUUID():
  28. 2. nameUUIDFromBytes():
  29. 3. fromString():
  30. Comparing two UUIDs:
  31. Other Methods:
  32. 1. getLeastSignificantBits() And getMostSignificantBits():
  33. 2. variant() And version():
  34. Working with a Time-Based UUID (v1):
  35. Conclusion:

Java uuid from bytes

UUID represents a Universally Unique Identifier per RFC 4122. See the RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace for more information.

Version: $Revision: 480488 $ $Date: 2006-11-29 08:57:26 +0000 (Wed, 29 Nov 2006) $ Author: Commons-Id Team See Also: Serialized Form

Field Summary
Fields inherited from interface org.apache.commons.id.uuid.Constants
CLOCK_SEQ_HI_AND_RESERVED_BYTE_8, FORMAT_POSITION1, FORMAT_POSITION2, FORMAT_POSITION3, FORMAT_POSITION4, MD5_ENCODING, SHA1_ENCODING, TIME_HI_AND_VERSION_BYTE_6, TIME_HI_BYTE_LEN, TIME_HI_START_POS, TIME_HI_TS_POS, TIME_LOW_BYTE_LEN, TIME_LOW_START_POS, TIME_LOW_TS_POS, TIME_MID_BYTE_LEN, TIME_MID_START_POS, TIME_MID_TS_POS, TOKEN_LENGTHS, TOKENS_IN_UUID, URN_PREFIX, UUID_BIT_LENGTH, UUID_BYTE_LENGTH, UUID_FORMATTED_LENGTH, UUID_UNFORMATTED_LENGTH, VARIANT_FUTURE, VARIANT_IETF_DRAFT, VARIANT_MS, VARIANT_NCS_COMPAT, VERSION_FIVE, VERSION_FOUR, VERSION_ONE, VERSION_THREE, VERSION_TWO, WRONG_VAR_VER_MSG
Constructor Summary
UUID ()
Constructs a nil UUID
UUID (byte[] byteArray)
Constructs a UUID from a 16 byte array.
UUID (java.io.DataInput input)
Constructs a UUID from a DataInput.
UUID (long mostSignificant, long leastSignificant)
Constructs a UUID from two long values in most significant byte, and least significant bytes order.
UUID (java.lang.String uuidString)
Constructs a UUID from a UUID formatted String.
UUID (UUID copyFrom)
Copy constructor.
Method Summary
int clockSequence ()
Returns the clock sequence value in the UUID.
int compareTo (java.lang.Object compareTo)
Compares two UUID’s for equality.
boolean equals (java.lang.Object obj)
Compares two UUID for equality.
static UUID fromString (java.lang.String uuidString)
Parses a string for a UUID.
byte[] getRawBytes ()
Returns a copy of the byte values contained in this UUID.
int hashCode ()
Returns a hash code value for the object.
static UUID nameUUIDFromString (java.lang.String name, UUID namespace)
Returns a new version three UUID given a name and the namespace’s UUID.
static UUID nameUUIDFromString (java.lang.String name, UUID namespace, java.lang.String encoding)
Returns a new version three (MD5) or five (SHA-1) UUID, using the specified encoding given a name and the namespace’s UUID.
long node ()
Returns the node identifier found in this UUID.
static UUID randomUUID ()
Returns a new version 4 UUID, based upon Random bits.
long timestamp ()
Returns the timestamp value of the UUID as 100-nano second intervals since the Gregorian change offset (00:00:00.00, 15 October 1582 ).
static UUID timeUUID ()
Returns a new version 1 UUID, based upon node identifier and time stamp.
java.lang.String toString ()
Returns a string representation of the UUID.
java.lang.String toUrn ()
Returns a urn representation of the UUID.
int variant ()
Returns the variant field of the UUID.
int version ()
Returns the version of the UUID.
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

UUID


UUID

Parameters: copyFrom — the UUID to copy to create this UUID.

UUID

public UUID(byte[] byteArray) throws java.lang.IllegalArgumentException

Constructs a UUID from a 16 byte array.

Parameters: byteArray — the 16 byte array to construct this UUID from. Throws: java.lang.IllegalArgumentException — argument must be 16 bytes

UUID

public UUID(java.io.DataInput input) throws java.io.IOException

Constructs a UUID from a DataInput. Note if 16 bytes are not available this method will block.

Parameters: input — the datainput with 16 bytes to read in from. Throws: java.io.IOException — exception if there is an IO problem also argument must contain 16 bytes.

UUID

public UUID(long mostSignificant, long leastSignificant)

Constructs a UUID from two long values in most significant byte, and least significant bytes order.

Parameters: mostSignificant — — the most significant 8 bytes of the uuid to be constructed. leastSignificant — — the least significant 8 bytes of the uuid to be constructed.

UUID

Constructs a UUID from a UUID formatted String.

Parameters: uuidString — the String representing a UUID to construct this UUID Throws: UUIDFormatException — String must be a properly formatted UUID string

Method Detail

fromString

public static UUID fromString(java.lang.String uuidString) throws UUIDFormatException

Parses a string for a UUID.

Parameters: uuidString — the UUID formatted String to parse. Returns: Returns a UUID or null if the formatted string could not be parsed. Throws: UUIDFormatException — the String must be a properly formatted UUID String.

toString

public java.lang.String toString()

Returns a string representation of the UUID.

Overrides: toString in class java.lang.Object Returns: a string representation of the UUID formatted according to the specification.

toUrn

public java.lang.String toUrn()

Returns a urn representation of the UUID. This is same as the toString() value prefixed with urn:uuid:

Returns: Returns the urn string representation of the UUID

equals

public boolean equals(java.lang.Object obj)

Compares two UUID for equality.

Overrides: equals in class java.lang.Object See Also: Object.equals(Object)

hashCode

Returns a hash code value for the object.

Overrides: hashCode in class java.lang.Object See Also: Object.hashCode()

compareTo

public int compareTo(java.lang.Object compareTo) throws java.lang.ClassCastException

Compares two UUID’s for equality.

Specified by: compareTo in interface java.lang.Comparable Throws: java.lang.ClassCastException See Also: Comparable.compareTo(Object)

clockSequence

public int clockSequence() throws java.lang.UnsupportedOperationException

Returns the clock sequence value in the UUID. The clock sequence is a random assigned to a particular clock instance that generated the time in the timestamp of a time based UUID.

Returns: the clock sequence value in the UUID. Throws: java.lang.UnsupportedOperationException — thrown if this is not a IETF variant or not a time-based UUID.

version

  • VERSION_ONE — The time-based version
  • VERSION_TWO — DCE Security version, with embedded POSIX UIDs.
  • VERSION_THREE — Name based UUID with MD5 hashing.
  • VERSION_FOUR — Random based UUID.
  • VERSION_FIVE — Name based UUID with SHA-1 hashing.

Returns: the version of the UUID.

variant

Returns the variant field of the UUID.

node

public long node() throws java.lang.UnsupportedOperationException

Returns the node identifier found in this UUID. The specification was written such that this value holds the IEEE 802 MAC address. The specification permits this value to be calculated from other sources other than the MAC.

Returns: the node identifier found in this UUID. Throws: java.lang.UnsupportedOperationException — thrown if this is not a IETF variant or not a time-based UUID.

timestamp

public long timestamp() throws java.lang.UnsupportedOperationException

Returns the timestamp value of the UUID as 100-nano second intervals since the Gregorian change offset (00:00:00.00, 15 October 1582 ).

Returns: the timestamp value of the UUID as 100-nano second intervals since the Gregorian change offset. Throws: java.lang.UnsupportedOperationException — thrown if this is not a IETF variant or not a time-based UUID.

getRawBytes

Returns a copy of the byte values contained in this UUID.

Returns: a copy of the byte values contained in this UUID.

randomUUID

Returns a new version 4 UUID, based upon Random bits.

Returns: a new version 4 UUID, based upon Random bits.

timeUUID

Returns a new version 1 UUID, based upon node identifier and time stamp.

Returns: a new version 1 UUID, based upon node identifier and time stamp.

nameUUIDFromString

public static UUID nameUUIDFromString(java.lang.String name, UUID namespace, java.lang.String encoding)

Returns a new version three (MD5) or five (SHA-1) UUID, using the specified encoding given a name and the namespace’s UUID.

Parameters: name — String the name to calculate the UUID for. namespace — UUID assigned to this namespace. encoding — The encoding to use, either # or # Returns: a new version three UUID given a name and the namespace’s UUID.

nameUUIDFromString

public static UUID nameUUIDFromString(java.lang.String name, UUID namespace)

Returns a new version three UUID given a name and the namespace’s UUID.

Parameters: name — String the name to calculate the UUID for. namespace — UUID assigned to this namespace. Returns: a new version three UUID given a name and the namespace’s UUID.

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Java UUID

UUID (Universal Unique Identifier) represents a 128-bit long unique value. It’s also popularly known as GUID (Globally Unique Identifier). The standard representation of UUID is made up of hexadecimal digits:

533a4559-e55c-18b3-8456-555563322002

And has 36 characters that include four hyphens ‘-‘. java.util.UUID class in Java represents an immutable UUID. We can use UUID class for generating a random file name, a session or a transaction id. Another popular usage of UUID is for generating primary key values in the database. Java UUID class has a method for manipulating the Leach-Salz variant (variant 2). However, its constructor allows for generating any type of UUID:

new UUID(long mostSigBits, long leastSigBits)

UUID Versions and Variants:

533a4559-e55c-18b3-8456-555563322002 xxxxxxxx-xxxx-Bxxx-Axxx-xxxxxxxxxxxx

Here, the value of A represents the variant and is determined by its first three MSBs (Most-Significant bits):

MSB1 MSB2 MSB3 Variant Variant Description
0 X X 0 Reserved for NCS backward compatibility
1 0 X 2 Leach-Salz
1 1 0 6 Reserved, Microsoft Corporation backward compatibility
1 1 7 Reserved for future definition

For us, A = 8 (1000), so the first three MSBs are 100. That means our UUID has a variant of 2. For variant 2 UUIDs, there’re five different versions:

Version Description
v1 time-based
v2 DCE- Security
v3 and v5 name-based
v4 Randomly generated UUID

Generating a UUID:

1. randomUUID():

It generates a v4 pseudo-random UUID using a cryptographically strong pseudo-random number generator:

UUID uuid = UUID.randomUUID();

2. nameUUIDFromBytes():

byte[] byteArr = ; UUID uuid = UUID.nameUUIDFromBytes(byteArr);

3. fromString():

UUID uuid = UUID.fromString("533a4559-e55c-18b3-2456-555563322002");

It’ll throw an IllegalArgumentException for any invalid string passed in as an argument.

Comparing two UUIDs:

Java UUID class implements Comparable interface. So, we can use the compareTo()method to compare them:

UUID uuid1 = UUID.randomUUID(); UUID uuid2 = UUID.randomUUID(); int result = uuid1.compareTo(uuid2);
  • 1: if uuid1 is greater than uuid2
  • 0: if uuid1 = uuid2
  • -1: if uuid1 is less than that of uuid2

We can optionally use the equals() method for comparison as well.

Other Methods:

Let’s cover a few other methods of the Java UUID class:

1. getLeastSignificantBits() And getMostSignificantBits():

As the name suggests, getLeastSignificantBits() and getMostSignificantBits() return the 64 least-significant and 64 most-significant bits respectively:

UUID uuid = UUID.randomUUID(); long leastSignificantBits = uuid.getLeastSignificantBits(); long mostSignificantBits = uuid.getMostSignificantBits();

Both of these methods return a long value.

2. variant() And version():

We can also query the variant and the version of a UUID:

UUID uuid = UUID.randomUUID(); int variant = uuid.variant(); int version = uuid.version();

Working with a Time-Based UUID (v1):

Let’s start by adding a dependency to java-uuid-generator in our POM:

 com.fasterxml.uuid java-uuid-generator 3.1.5

Note that this library provides various types of UUID generators.

To create a time-based UUID, we’ll have:

UUID uuid = Generators.timeBasedGenerator().generate();

Other methods from the java.util package that comes handy when dealing with v1 UUIDs’include:

1. timestamp(): Returns a timestamp value associated with a given v1 UUID. This method will throw a UnsupportedOperationException when used with any other types of UUID.

2. clockSequence(): It returns a 14-bit value constructed from the clock sequence field of a given UUID. It’ll also throw an UnsupportedOperationException for UUIDs other than of type v1.

Conclusion:

In this tutorial, we learned about what a UUID is and its variants. We talked about different available versions for the variant type 2. We also covered a lot of methods exposed by the Java UUID class.

Published on Java Code Geeks with permission by Shubhra Srivastava, partner at our JCG program. See the original article here: Java UUID

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