Collection Framework Interview Questions

1. What is Java Collections Framework? List out some benefits of Collections framework?

2. What are the basic interfaces of Java Collections Framework?

3.   What is an Iterator?

4.   What is difference between Enumeration and Iterator interface ?

5.   What are different ways to iterate over a list?

6.   How  Hashset   works  internally ?

7.  What is difference between HashMap and Hashtable?  

8.   What is difference between Arraylist and Vector?

9.  What  is difference between Arraylist and Linklist?            

10. What difference between HashMap and TreeMap ?

11. Can a Hash Map  have multiple key  same type ?

12. Which collection classes are thread-safe?

13. What is Comparable and Comparator interface?

14. How can we create a synchronised collection from given collection?

15. What is difference between collections and collection ?

16. How Generics  helpful  in Collection Framework?

17. What  is toArray() ,  sort(), keyset() methods ?

18. How you find out  common elements  in two list and set ?

19. What is diffrence between  Hashmap  and ConcurrentHashMap?

20 .How  HashMap works   Internally ?                       

21 What  is   difference Array  and ArrayList?

22.  What  is  difference  between List  and  LinkList ?

23 . How to convert Array in to ArrayList?                   

24.  What is use   of generics  in Collection?

25. List some collection classes and Interfaces?

26. What is difference between List and Set ?

27. What is difference between HashSet and  TreeSet?. When to prefer TreeSet
      over HashSet ?

28   What  is  difference  between   Compactor  and Comparable  Interface ?    

29  How   to   short   employees  according to age ?    

30  What is  fail safe and fail fast.

31 . How  HashMap   and  TreeMap    differ ? what  time complexity of   TreeMap and HashMap ?