corejava3

11. What are the important methods of StringTokenizer?

hasMoreTokens()

nextToken()

countToken()

which will use to display string which get split.

12. Is ++ operator is thread-safe in Java? 
 No .Its because it  involve multiple instructions like reading a value, incrementing it and storing it back into memory which may lead to overlapping between multiple threads.

13. What is the size of int in 64-bit JVM?
The size of an int variable is constant in Java irrespective of platform.

Its size will always be 32 bits.

14. LinkedList in Java is doubly or singly linked list?
It's a doubly linked list.

15. Does constructor return any value?

Yes, implicitly it returns current instance.