JUG is a set of Java classes for working with UUIDs: generating UUIDs using any of standard methods, outputting efficiently, sorting and so on. It generates UUIDs according to the UUID specification (RFC-4122) (also see Wikipedia UUID page for more explanation)
JUG was written by Tatu Saloranta (tatu.saloranta@iki.fi) originally in 2002 and has been updated over the years.
In addition, many other individuals have helped fix bugs and implement new features: please see release-notes/CREDITS for the complete list.
JUG is licensed under Apache License 2.0.
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JUG can be used as a command-line tool (via class com.fasterxml.uuid.Jug),
or as a pluggable component.
Maven coordinates are:
<dependency>
<groupId>com.fasterxml.uuid</groupId>
<artifactId>java-uuid-generator</artifactId>
<version>4.0.1</version>
</dependency>The only dependency for JUG is the logging library:
- For versions up to 3.x,
log4jis used, optionally (runtime dependency) - For versions 4.x and up,
slf4jAPI is used: logging implementation to be provided by calling application
Since version 3.2.0, JUG defines JDK9+ compatible module-info.class, with module name of com.fasterxml.uuid.
For direct downloads, check out Project Wiki.
The original use case for JUG was generation of UUID values. This is done by first selecting a kind of generator to use, and then calling its generate() method.
For example:
UUID uuid = Generators.randomBasedGenerator().generate();
UUID uuid = Generators.timeBasedGenerator().generate();If you want customize generators, you may also just want to hold on to generator instance:
TimeBasedGenerator gen = Generators.timeBasedGenerator(EthernetAddress.fromInterface());
UUID uuid = gen.generate();
UUID anotherUuid = gen.generate();Generators are fully thread-safe, so a single instance may be shared among multiple threads.
Javadocs for further information can be found from Project Wiki.
Sometimes you may want to convert from java.util.UUID into external serialization:
for example, as Strings or byte arrays (byte[]).
Conversion to String is easy with UUID.toString() (provided by JDK), but there is no similar functionality for converting into byte[].
But UUIDUtil class provides methods for efficient conversions:
byte[] asBytes = UUIDUtil.asByteArray(uuid);
// or if you have longer buffer already
byte[] outputBuffer = new byte[1000];
// append at position #100
UUIDUtil.toByteArray(uuid, outputBuffer, 100);
UUID values are often passed as java Strings or byte[]s (byte arrays),
and conversion is needed to get to actual java.util.UUID instances.
JUG has optimized conversion functionality available via class UUIDUtil (package
com.fasterxml.uuid.impl), used as follows:
UUID uuidFromStr = UUIDUtil.uuid("ebb8e8fe-b1b1-11d7-8adb-00b0d078fa18");
byte[] rawUuidBytes = ...; // byte array with 16 bytes
UUID uuidFromBytes = UUIDUtil.uuid(rawUuidBytes)
Note that while JDK has functionality for constructing UUID from String, like so:
UUID uuidFromStr = UUID.fromString("ebb8e8fe-b1b1-11d7-8adb-00b0d078fa18");
it is rather slower than JUG version: for more information, read Measuring performance of Java UUID.fromString().
JUG versions 3.1 and later require JDK 1.6 to work, mostly to be able to access local Ethernet MAC address.
Earlier versions (3.0 and before) worked on 1.4 (which introduced java.util.UUID).
JDK's java.util.UUID has flawed implementation of compareTo(), which uses naive comparison
of 64-bit values. This does NOT work as expected, given that underlying content is for all purposes
unsigned. For example two UUIDs:
7f905a0b-bb6e-11e3-9e8f-000000000000
8028f08c-bb6e-11e3-9e8f-000000000000
would be ordered with second one first, due to sign extension (second value is considered to be negative, and hence "smaller").
Because of this, you should always use external comparator, such as
com.fasterxml.uuid.UUIDComparator, which implements expected sorting order that is simple
unsigned sorting, which is also same as lexicographic (alphabetic) sorting of UUIDs (when
assuming uniform capitalization).
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There are many other publicly available UUID generators. For example:
- Apache Commons IO has UUID generator
- eaio-uuid
- JDK has included
java.util.UUIDsince 1.4, but omits generation methods (esp. time/location based ones), has sub-standard performance for many operations and implements comparison in useless way - ohannburkard.de UUID generator
Note that although some packages claim to be faster than others, it is not clear whether:
- Claims have been properly verified (or, if they have, can be independently verified), AND
- It is not likely that performance differences truly matter: JUG, for example, can generate a millions of UUID per second per core (sometimes hitting the theoretical limit of 10 million per second) -- and it seems unlikely that generation will be bottleneck for about any use case
so it is often best to choose based on stability of packages and API.