Core java fundamental interview questions

1. In the non-static method, the reference to the instance of the enclosing context is passed implicitly in the constructor call of the non-static local class
2.  Equals , comparable and comparator - http://leepoint.net/notes-java/data/expressions/22compareobjects.html
3. Common Question - http://bateru.com/news/2011/03/484/
4.  Common question - http://www.fromdev.com/2010/08/10-jdbc-questions-for-java-beginners.html
5. Good questions - http://javarevisited.blogspot.in/2011/04/top-20-core-java-interview-questions.html
6. Multithreading  - http://www.fromdev.com/2008/05/java-threading-questions.html
7. Collection - http://www.fromdev.com/2008/05/java-collections-questions.html
8. Classpath - http://www.fromdev.com/2012/09/Java-Path-Classpath-Questions-Answers.html
9. Jdbc - http://www.fromdev.com/2010/08/10-jdbc-questions-for-java-beginners.html
10.  Why static method override is not allowed
11. Starting thread more than once - http://stackoverflow.com/questions/1215548/is-it-legal-to-call-the-start-method-twice-on-the-same-thread
12. Wait notify- notify all - http://javarevisited.blogspot.sg/2011/05/wait-notify-and-notifyall-in-java.html 
13. Volatile vs synchronization - http://javarevisited.blogspot.in/2011/06/volatile-keyword-java-example-tutorial.html
14. HashTable vs Concurrent HashMap vs SyncronizedMap - http://javarevisited.blogspot.sg/2011/04/difference-between-concurrenthashmap.html
15. HashSet Vs TreeSet -http://java67.blogspot.sg/2012/08/difference-between-hashset-and-treeset-java.html
16.  http://javarevisited.blogspot.sg/2011/08/what-is-polymorphism-in-java-example.html
17. http://java67.blogspot.sg/2012/08/difference-between-string-and-stringbuffer-in-java.html
18. http://javarevisited.blogspot.sg/2012/01/how-to-reverse-string-in-java-using.html
19. http://java67.blogspot.sg/2012/09/java-collection-interview-questions.html
20. http://java67.blogspot.sg/2012/09/what-is-new-in-java-7-top-5-jdk-7.html
21. http://java67.blogspot.sg/2012/08/10-java-coding-interview-questions-and.html
22. http://java67.blogspot.sg/2012/08/5-thread-interview-questions-answers-in.html
23. http://java67.blogspot.sg/2012/09/top-10-tough-core-java-interview-questions-answers.html
24. http://javarevisited.blogspot.in/2011/11/collection-interview-questions-answers.html
25. http://javarevisited.blogspot.in/2011/02/how-hashmap-works-in-java.html
26. http://javarevisited.blogspot.in/2011/04/top-20-core-java-interview-questions.html
27. http://javarevisited.blogspot.in/2012/12/difference-between-equals-method-and-equality-operator-java.html
28. http://javarevisited.blogspot.sg/2011/04/difference-between-concurrenthashmap.html
29. http://java67.blogspot.in/2012/09/java-collection-interview-questions.html

Other important questions - 

1. What are advantages and disadvantages of singleton
2. Fail safe and fail fast iterator & internal working on fail fast iterator
3. The way to synchronize hash map-
• By passing it to the constructor of HashMap
• By passing it to the constructor of HashTable
• By calling synchronizedMap method of collections class
• By providing custom synchronized implementation
4. ClassNotFoundException Vs NoClassDefFoundError
5. What is stackOverFlow Error and can it be caught 
6. New features in Java7
7. Caching on wrapper classes

Serialization interview questions - 

http://stackoverflow.com/questions/447898/what-is-object-serialization
http://javarevisited.blogspot.sg/2011/04/top-10-java-serialization-interview.html

http://www.fromdev.com/2012/06/15-java-serialization-interview.html

http://java-questions.com/Serialization-interview-questions.html

OCPJP topics