Create a GUID in Java

Question

What are some of the best ways to create a GUID in Java

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It depends what kind of UUID you want    The standard Java UUID class generates Version 4  random  UUIDs    UPDATE - Version 3  name  UUIDs can also be generated   It can also handle other variants  though it cannot generate them    In this case   handle  means construct UUID instances from long  byte   or String representations  and provide some appropriate accessors   The Java UUID Generator  JUG  implementation purports to support  all 3  official  types of UUID as defined by RFC-4122      though the RFC actually defines 4 types and mentions a 5th type    For more information on UUID types and variants  there is a good summary in Wikipedia  and the gory details are in RFC 4122 and the other specifications

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Have a look at the UUID class bundled with Java 5 and later    For example    If you want a random UUID you can use the randomUUID method  If you want a UUID initialized to a specific value you can use the UUID constructor or the fromString method

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java util UUID randomUUID

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This answer contains 2 generators for random-based and name-based UUIDs  compliant with RFC-4122  Feel free to use and share  RANDOM-BASED  v4  This utility class that generates random-based UUIDs  package your package name   import java security SecureRandom  import java util Random  import java util UUID          Utility class that creates random-based UUIDs          public abstract class RandomUuidCreator        private static final int RANDOM VERSION   4                  Returns a random-based UUID                 It uses a thread local   link SecureRandom                   return a random-based UUID             public static UUID getRandomUuid             return getRandomUuid SecureRandomLazyHolder THREAD LOCAL RANDOM get                           Returns a random-based UUID                 It uses any instance of   link Random                   return a random-based UUID             public static UUID getRandomUuid Random random             long msb   0          long lsb   0               3  set all bit randomly         if  random instanceof SecureRandom                   Faster for instances of SecureRandom             final byte   bytes   new byte 16               random nextBytes bytes               msb   toNumber bytes  0  8      first 8 bytes for MSB             lsb   toNumber bytes  8  16      last 8 bytes for LSB           else               msb   random nextLong       first 8 bytes for MSB             lsb   random nextLong       last 8 bytes for LSB                       Apply version and variant bits  required for RFC-4122 compliance          msb    msb  amp  0xffffffffffff0fffL     RANDOM VERSION  amp  0x0f   lt  lt  12     apply version bits         lsb    lsb  amp  0x3fffffffffffffffL    0x8000000000000000L     apply variant bits             Return the UUID         return new UUID msb  lsb              private static long toNumber final byte   bytes  final int start  final int length            long result   0          for  int i   start  i  lt  length  i                  result    result  lt  lt  8     bytes i   amp  0xff                     return result                Holds thread local secure random     private static class SecureRandomLazyHolder           static final ThreadLocal lt Random gt  THREAD LOCAL RANDOM   ThreadLocal withInitial SecureRandom  new                         For tests              public static void main String   args             System out println  quot    Using thread local  java security SecureRandom   DEFAULT  quot            System out println  quot RandomUuidCreator getRandomUuid   quot            System out println            for  int i   0  i  lt  5  i                  System out println RandomUuidCreator getRandomUuid                        System out println            System out println  quot    Using  java util Random   FASTER  quot            System out println  quot RandomUuidCreator getRandomUuid new Random    quot            System out println            Random random   new Random            for  int i   0  i  lt  5  i                  System out println RandomUuidCreator getRandomUuid random                       This is the output     Using thread local  java security SecureRandom   DEFAULT  RandomUuidCreator getRandomUuid     ef4f5ad2-8147-46cb-8389-c2b8c3ef6b10   adc0305a-df29-4f08-9d73-800fde2048f0   4b794b59-bff8-4013-b656-5d34c33f4ce3   22517093-ee24-4120-96a5-ecee943992d1   899fb1fb-3e3d-4026-85a8-8a2d274a10cb      Using  java util Random   FASTER  RandomUuidCreator getRandomUuid new Random      4dabbbc2-fcb2-4074-a91c-5e2977a5bbf8   078ec231-88bc-4d74-9774-96c0b820ceda   726638fa-69a6-4a18-b09f-5fd2a708059b   15616ebe-1dfd-4f5c-b2ed-cea0ac1ad823   affa31ad-5e55-4cde-8232-cddd4931923a   NAME-BASED  v3 and v5  This utility class that generates name-based UUIDs  MD5 and SHA1   package your package name   import java nio charset StandardCharsets  import java security MessageDigest  import java security NoSuchAlgorithmException  import java util UUID          Utility class that creates UUIDv3  MD5  and UUIDv5  SHA1          public class HashUuidCreator           Domain Name System     public static final UUID NAMESPACE DNS   new UUID 0x6ba7b8109dad11d1L  0x80b400c04fd430c8L          Uniform Resource Locator     public static final UUID NAMESPACE URL   new UUID 0x6ba7b8119dad11d1L  0x80b400c04fd430c8L          ISO Object ID     public static final UUID NAMESPACE ISO OID   new UUID 0x6ba7b8129dad11d1L  0x80b400c04fd430c8L          X 500 Distinguished Name     public static final UUID NAMESPACE X500 DN   new UUID 0x6ba7b8149dad11d1L  0x80b400c04fd430c8L        private static final int VERSION 3   3     UUIDv3 MD5     private static final int VERSION 5   5     UUIDv5 SHA1      private static final String MESSAGE DIGEST MD5    quot MD5 quot      UUIDv3     private static final String MESSAGE DIGEST SHA1    quot SHA-1 quot      UUIDv5      private static UUID getHashUuid UUID namespace  String name  String algorithm  int version             final byte   hash          final MessageDigest hasher           try                  Instantiate a message digest for the chosen algorithm             hasher   MessageDigest getInstance algorithm                   Insert name space if NOT NULL             if  namespace    null                    hasher update toBytes namespace getMostSignificantBits                      hasher update toBytes namespace getLeastSignificantBits                                    Generate the hash             hash   hasher digest name getBytes StandardCharsets UTF 8                    Split the hash into two parts  MSB and LSB             long msb   toNumber hash  0  8      first 8 bytes for MSB             long lsb   toNumber hash  8  16      last 8 bytes for LSB                 Apply version and variant bits  required for RFC-4122 compliance              msb    msb  amp  0xffffffffffff0fffL     version  amp  0x0f   lt  lt  12     apply version bits             lsb    lsb  amp  0x3fffffffffffffffL    0x8000000000000000L     apply variant bits                 Return the UUID             return new UUID msb  lsb              catch  NoSuchAlgorithmException e                throw new RuntimeException  quot Message digest algorithm not supported  quot                         public static UUID getMd5Uuid String string            return getHashUuid null  string  MESSAGE DIGEST MD5  VERSION 3              public static UUID getSha1Uuid String string            return getHashUuid null  string  MESSAGE DIGEST SHA1  VERSION 5              public static UUID getMd5Uuid UUID namespace  String string            return getHashUuid namespace  string  MESSAGE DIGEST MD5  VERSION 3              public static UUID getSha1Uuid UUID namespace  String string            return getHashUuid namespace  string  MESSAGE DIGEST SHA1  VERSION 5              private static byte   toBytes final long number            return new byte      byte   number  gt  gt  gt  56    byte   number  gt  gt  gt  48    byte   number  gt  gt  gt  40                    byte   number  gt  gt  gt  32    byte   number  gt  gt  gt  24    byte   number  gt  gt  gt  16    byte   number  gt  gt  gt  8                    byte   number                private static long toNumber final byte   bytes  final int start  final int length            long result   0          for  int i   start  i  lt  length  i                  result    result  lt  lt  8     bytes i   amp  0xff                     return result                        For tests              public static void main String   args             String string    quot JUST A TEST STRING quot           UUID namespace   UUID randomUUID       A custom name space          System out println  quot Java s generator quot            System out println  quot UUID nameUUIDFromBytes           quot    UUID nameUUIDFromBytes string getBytes       quot   quot            System out println            System out println  quot This generator quot            System out println  quot HashUuidCreator getMd5Uuid       quot    HashUuidCreator getMd5Uuid string     quot   quot            System out println  quot HashUuidCreator getSha1Uuid      quot    HashUuidCreator getSha1Uuid string     quot   quot            System out println            System out println  quot This generator WITH name space quot            System out println  quot HashUuidCreator getMd5Uuid       quot    HashUuidCreator getMd5Uuid namespace  string     quot   quot            System out println  quot HashUuidCreator getSha1Uuid      quot    HashUuidCreator getSha1Uuid namespace  string     quot   quot              This is the output     Java s generator UUID nameUUIDFromBytes          9e120341-627f-32be-8393-58b5d655b751      This generator HashUuidCreator getMd5Uuid      9e120341-627f-32be-8393-58b5d655b751  HashUuidCreator getSha1Uuid     e4586bed-032a-5ae6-9883-331cd94c4ffa      This generator WITH name space HashUuidCreator getMd5Uuid      2b098683-03c9-3ed8-9426-cf5c81ab1f9f  HashUuidCreator getSha1Uuid     1ef568c7-726b-58cc-a72a-7df173463bbb   ALTERNATE GENERATOR You can also use the uuid-creator library  See these examples     Create a random-based UUID UUID uuid   UuidCreator getRandomBased        Create a name based UUID  SHA1  String name    quot JUST A TEST STRING quot   UUID uuid   UuidCreator getNameBasedSha1 name    Project page  https   github com f4b6a3 uuid-creator

User · Answer

The other Answers are correct  especially this one by Stephen C   Reaching Outside Java  Generating a UUID value within Java is limited to Version 4  random  because of security concerns    If you want other versions of UUIDs  one avenue is to have your Java app reach outside the JVM to generate UUIDs by calling on    Command-line utilityBundled with nearly every operating system  For example  uuidgen found in Mac OS X  BSD  and Linux  Database serverUse JDBC to retrieve a UUID generated on the database server For example  the uuid-ossp extension often bundled with Postgres  That extension can generates Versions 1  3  and 4 values and additionally a couple variations    uuid generate v1mc        generates a version 1 UUID but uses a random multicast MAC address instead of the real MAC address of the computer  uuid generate v5 namespace uuid  name text       generates a version 5 UUID  which works like a version 3 UUID except that SHA-1 is used as a hashing method   Web ServiceFor example  UUID Generator creates Versions 1  amp  3 as well as nil values and GUID

User · Answer

Just to extend Mark Byers s answer with an example   import java util UUID   public class RandomStringUUID       public static void main String   args            UUID uuid   UUID randomUUID            System out println  UUID     uuid toString

[java] Create a GUID in Java

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