Thread safe unique sequence generation

[narayana_giri]

Please let me know what is the best and simple thread safe unique sequence generation approach.

Appreciate response with links/sample code.

[kaynezhang]

If you want your  sequence generation class to be survived between server restart ,you  can consider to use db seqence(oracle sequence,mysql  LAST_INSERT_ID() ..)
If not,You can use Atomic Integer ,it is thread safe.you can define a singleton class and use AtomicInteger 's getAndIncrement() method to generate sequence number.