Java

1. SpringMVC
2. OOPS
3. Collections
1. How Hashset and Hashmap is implemented
2. Importance of hashcode() and equals()
3. Contract for hashcode and equals()
4. Concurrency package in java collections
1. What is ReadWrite Lock? Does ConcurrentHashMap uses ReadWrite Lock?
5. Comparator and Comparable
6. Making immutable object, 
4. Threading
1. Runnable vs Thread class
2. Executor service
3. Semaphore
4. Synchronization method and block
1. wait and notify. 
2. why wait and notify is added in Object class
5. print 1-2-3 
5. Serialization
1. serialVersionUID
2. Serializable and Externalizable interface
3. How to deal with Singleton along with Serialization
6. Exception Handling
1. in overriding scenario
7. Design Patterns
1. Builder