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UUID

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How to use UUID in Java and Android.

How to use UUID in Java and Android.

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  • 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