How to use UUID in Java and Android.

1. UUID
Tomoki Yamashita
2014.4.9 potatotips #6

2. Self-Introduction
• @tomorrowkey / Tomoki Yamashita
• Android Developer at COOKPAD
• http://blog.tomorrowkey.jp / 明日の

3. Agenda
• What is UUID?
• How to use it in Java
• Versions of UUID
• Which version can we use in Java
• To use version 1 in Java
• To use version 1 in Android

4. What is UUID

5. What is UUID?
• Universally Unique Identifier
• RFC 4122
• Generate Unique ID without servers.

6. How to use in
Java

7. How to use it in Java
import java.util.UUID;
public class Main {
public static void main(String... args) {
UUID uuid = UUID.randomUUID();
System.out.println(“uuid=” + uuid.toString());
}
}
#
53da3b97-075f-4bcd-af62-148b1a7d6712

8. Versions of UUID

9. Versions of UUID
• There are 5 versions of UUID.

10. Version 1
• Original version
• Use time(nano-seconds) and Mac
Address
• It won't duplicate because depends on
mac address.

11. Version 2
• Version for DCE(Distributed
Computing Environment) Security

12. Version 3
• Name and MD5 Hash
• If use the same name, it duplicate.

13. Version 4
• Random value
• It may not duplicate.

14. Version 5
• Name and SHA1 Hash
• If use the same name, it duplicate.

15. Which version can
we use in Java?

16. Which version can we
use in Java?
• Version 3
UUID.nameUUIDFromBytes(byte[] name)
• Version 4
UUID.randomUUID();

17. To use version1
in Java

18. To use version1
in Java
stephenc/eaio-uuid
https://github.com/stephenc/eaio-uuid

19. To use version1
in Java
build.gradle
compile ‘com.github.stephenc.eaio-uuid:uuid:3.4.0'
Main.java
com.eaio.uuid.UUID uuid = new com.eaio.uuid.UUID();
System.out.println(“uuid=” + uuid.toString());

20. To use version1
in Android

21. To use version1
in Android
build.gradle
compile ‘com.github.stephenc.eaio-uuid:uuid:3.4.0'
Main.java
com.eaio.uuid.UUID uuid = new com.eaio.uuid.UUID();
System.out.println(“uuid=” + uuid.toString());

22. To use version1
in Android
build.gradle
compile ‘com.github.stephenc.eaio-uuid:uuid:3.4.0'
Main.java
com.eaio.uuid.UUID uuid = new com.eaio.uuid.UUID();
System.out.println(“uuid=” + uuid.toString());
NoClassDefFoundError: com.eaio.uuid.UUID

23. Why...?
The library use a api which is not
supported in Android.
omg.CORBA.portable.IDLEntity

24. To use version1
in Android
• clone eaio-uuid
• remove CORBA api from source code.
• add a permission INTERNET

25. End
Understand principle about UUID and
then use it.
Thank you for listening

26. Referred links
RFC 4122 - A Universally Unique IDentifier (UUID) URN Namespace
http://tools.ietf.org/html/rfc4122
Universally unique identifier - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/UUID#Variants_and_versions
UUIDはなぜ、分散環境で好き勝手に生成しても衝突しないのか。RFC4122規格とUUIDの性質。 ¦ 三
度の飯とエレクトロン
http://blog.katty.in/5124