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# ULID Creator
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A Java library for generating ULIDs.
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* Generated in lexicographical order;
* Can be stored as a UUID/GUID;
* Can be stored as a string of 26 chars;
* String format is encoded to [Crockford's base32 ](https://www.crockford.com/base32.html );
* String format is URL safe, case insensitive and accepts hyphens.
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How to Use
------------------------------------------------------
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Create a ULID:
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```java
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UUID ulid = UlidCreator.getUlid(); // 01706d6c-6aad-c795-370c-98d0be881bba
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```
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Create a ULID string:
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```java
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String ulid = UlidCreator.getUlidString(); // 01E1PPRTMSQ34W7JR5YSND6B8Z
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```
### Maven dependency
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Add these lines to your `pom.xml` .
```xml
<!-- https://search.maven.org/artifact/com.github.f4b6a3/ulid - creator -->
< dependency >
< groupId > com.github.f4b6a3< / groupId >
< artifactId > ulid-creator< / artifactId >
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< version > 2.1.0< / version >
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< / dependency >
```
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See more options in [maven.org ](https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator ).
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Implementation
------------------------------------------------------
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### ULID
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The GUIDs in this library are based on the [ULID specification ](https://github.com/ulid/spec ). The first 48 bits represent the count of milliseconds since Unix Epoch, 1 January 1970. The remaining 60 bits are generated by a secure random number generator.
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Every time the timestamp changes the random part is reset to a new random value. If the current timestamp is equal to the previous one, the random bits are incremented by 1.
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The default random number generator is `java.security.SecureRandom` .
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```java
// GUID based on ULID spec
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UUID ulid = UlidCreator.getUlid();
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```
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Sequence of GUIDs based on ULID spec:
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```text
01706d6c-6aac-80bd-7ff5-f660c2dd58ea
01706d6c-6aac-80bd-7ff5-f660c2dd58eb
01706d6c-6aac-80bd-7ff5-f660c2dd58ec
01706d6c-6aac-80bd-7ff5-f660c2dd58ed
01706d6c-6aac-80bd-7ff5-f660c2dd58ee
01706d6c-6aac-80bd-7ff5-f660c2dd58ef
01706d6c-6aac-80bd-7ff5-f660c2dd58f0
01706d6c-6aac-80bd-7ff5-f660c2dd58f1
01706d6c-6aad-c795-370c-98d0be881bb8 < millisecond changed
01706d6c-6aad-c795-370c-98d0be881bb9
01706d6c-6aad-c795-370c-98d0be881bba
01706d6c-6aad-c795-370c-98d0be881bbb
01706d6c-6aad-c795-370c-98d0be881bbc
01706d6c-6aad-c795-370c-98d0be881bbd
01706d6c-6aad-c795-370c-98d0be881bbe
01706d6c-6aad-c795-370c-98d0be881bbf
^ look ^ look
|------------|---------------------|
millisecs randomness
```
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### ULID string
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The ULID string is a sequence of 26 chars. See the [ULID specification ](https://github.com/ulid/spec ) for more information.
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See the section on GUIDs to know how the 128 bits are generated in this library.
```java
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// String based on ULID spec
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String ulid = UlidCreator.getUlidString();
```
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Sequence of Strings based on ULID spec:
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```text
01E1PPRTMSQ34W7JR5YSND6B8T
01E1PPRTMSQ34W7JR5YSND6B8V
01E1PPRTMSQ34W7JR5YSND6B8W
01E1PPRTMSQ34W7JR5YSND6B8X
01E1PPRTMSQ34W7JR5YSND6B8Y
01E1PPRTMSQ34W7JR5YSND6B8Z
01E1PPRTMSQ34W7JR5YSND6B90
01E1PPRTMSQ34W7JR5YSND6B91
01E1PPRTMTYMX8G17TWSJJZMEE < millisecond changed
01E1PPRTMTYMX8G17TWSJJZMEF
01E1PPRTMTYMX8G17TWSJJZMEG
01E1PPRTMTYMX8G17TWSJJZMEH
01E1PPRTMTYMX8G17TWSJJZMEJ
01E1PPRTMTYMX8G17TWSJJZMEK
01E1PPRTMTYMX8G17TWSJJZMEM
01E1PPRTMTYMX8G17TWSJJZMEN
^ look ^ look
|---------|--------------|
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millisecs randomness
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```
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### How use the `UlidSpecCreator` directly
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These are some examples of using the `UlidSpecCreator` to create ULID strings:
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```java
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// with your custom timestamp strategy
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TimestampStrategy customStrategy = new CustomTimestampStrategy();
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UlidSpecCreator creator = UlidCreator.getUlidSpecCreator()
.withTimestampStrategy(customStrategy);
String ulid = creator.createString();
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```
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```java
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// with your custom random strategy that wraps any random generator
RandomStrategy customStrategy = new CustomRandomStrategy();
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UlidSpecCreator creator = UlidCreator.getUlidSpecCreator()
.withRandomStrategy(customStrategy);
String ulid = creator.createString();
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```
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```java
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// with `java.util.Random` number generator
Random random = new Random();
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UlidSpecCreator creator = UlidCreator.getUlidSpecCreator()
.withRandomGenerator(random);
String ulid = creator.createString();
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```
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Benchmark
------------------------------------------------------
This section shows benchmarks comparing `UlidCreator` to `java.util.UUID` .
```
---------------------------------------------------------------------------
THROUGHPUT Mode Cnt Score Error Units
---------------------------------------------------------------------------
Throughput.Java_RandomBased thrpt 5 2234,199 ± 2,844 ops/ms
Throughput.UlidCreator_Ulid thrpt 5 19155,742 ± 22,195 ops/ms
Throughput.UlidCreator_UlidString thrpt 5 4946,479 ± 22,800 ops/ms
---------------------------------------------------------------------------
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Total time: 00:04:01
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---------------------------------------------------------------------------
```
```
----------------------------------------------------------------------
AVERAGE TIME Mode Cnt Score Error Units
----------------------------------------------------------------------
AverageTime.Java_RandomBased avgt 5 449,641 ± 0,994 ns/op
AverageTime.UlidCreator_Ulid avgt 5 52,199 ± 0,185 ns/op
AverageTime.UlidCreator_UlidString avgt 5 202,014 ± 2,111 ns/op
----------------------------------------------------------------------
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Total time: 00:04:01
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----------------------------------------------------------------------
```
System: CPU i5-3330, 8G RAM, Ubuntu 20.04.
See: [uuid-creator-benchmark ](https://github.com/fabiolimace/uuid-creator-benchmark )
Links for generators
-------------------------------------------
* [UUID Creator ](https://github.com/f4b6a3/uuid-creator )
* [ULID Creator ](https://github.com/f4b6a3/ulid-creator )
* [TSID Creator ](https://github.com/f4b6a3/tsid-creator )