1) Which Java/JDK version you using ?
2) Could you please describe JDK 5 new features ?
3) Are you aware of new features added in JDK6 and JDK 7 ?
4) Have you used Multi-treading in java ? Could you please describe java concurrent collection libraries ?
5) what are blocking and non-blocking data structures ?
6) Different ways of synchronization in java like using Synchronized keyword, atomic operations, volatile etc ?