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Some basic interview question on collection. .......


Some basic interview question on collection. .......
Collection :-
===========
If u want to represent group of object's as a single entity then we have to use Collection
Collection Framework :-
= = = = = = = = = = = = = = =
It defines several class and interfaces which can be used to define collections
1.What is the difference between collection and map ?
Ans:-
Collection represents a group of individual objects
Map represents a group of key value pairs
2 . collection and Collections ?
Ans:-
Collection is an interface
Collections is a utility class which contain multiple method for collection
Collections class defines several utility methods for collection objects like
Collections.sort ( al );
3 . what is the main purpose of generics
Ans:-
The main objective of generics are to provide type safety under to resolve type casting problems
4. difference between list and set ?
5 . what is cursor and how many cursor are available in java?
6 . what is the need of concurent collection
Ans:-
-Most of the traditional collection objects are not thread safe
-already existing thread safe collection like (vector and hashTable ) performance wise not good
-while one thread iterating collection the other threads are not allowed to modify collection objects from underlying collection. U will get ConcurrentModificationException
To overcome this problem sun people develop concurent collection in 1.5 versions
Concurent collection always thread safe
Concurent collection are good in performance with respect to traditional collection
While one thread iterating collection the other thread are allowed to modify underlying collection in safe manner, concurent collection never throw ConcurentModificationException
7 . Explain about ConcurentModificationException?
Ans:-
In traditional collection like Arraylist while one thread iterating collection if other threads are trying to modify then we will get ConcurrentModificationException
8 . what are various concurent collection ?
Ans:-
CopyOnWriteArrayList
CopyOnWriteArraySet
ConcurentHashMap
9 . what is the difference between fail fast and fail safe iterator
Fail-fast:-
= = = = = = = = = = = = = = = =
-while one thread iterating collection if other threads trying to modify collection then iterator fails by raising ConcurentModificationException
Such type of iterator are called fail-fast iterator
Ex - iterator of any traditional collection like Arraylist, vector etc
.fail-safe:-
= = = = = = = = = = = = = = = =
While one thread iterating collection if other threads are allowed to modify underlying collection in shape manner such type of Iterator r called fail safe iterator. In this case we won't get ConcurrentModificationException
Ex:-iterator of any concurent collection

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