Question Answer Tutorial - JAVA->Collection

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Question: What is Collection?

Answer: Collection is a framework which is used to put a g
roup of objects togather.

Question: What is Collections in Java?

Answer: Collections in java is a framework that provides an arc
hitecture to store and manipulate the group/>of objects. All the operations that you perform on a&
nbsp;data such as searching, sorting, insertion,/>manipulation, deletion etc. can be performed by Java Colle
ctions. Java Collection simply means a/>single unit of objects. Java Collection framework provides
;many interfaces (Set, List, Queue, Deque/>etc.) and classes (ArrayList, Vector, LinkedList, PriorityQueue,&nbs
p;HashSet, LinkedHashSet, TreeSetetc).

Question: What is the Hierarchy of Collection Framework?

Answer: The hierarchy of collection framework is as follows:/>##ImageTag##CollectionHierarchy_QATutorials.JPG##Collection Framework Hierarchy

/>/>/>/>/>/>/>/>/>/>
/>/>/>/>

Question: What are the important methods in Collection Interface?

Answer: There are many methods declared in the Collection interface.
They importatnt methods are asfollows:/>

No.

Method

Description

1 public boolean add(Object element)

It is used to&n
bsp;insert an element in thiscollection

2 public boolean addAll(collection c)

It is used to&
nbsp;insert the specified collection/>elements in the invoking collection

3 public boolean remove(Object element)

It is used t
o delete an element from thiscollection

4 public boolean removeAll(Collection c)

It is used
to delete all the elements of/>specified collection from the invoking collection

5 public boolean retainAll(Collection c)

It is used
to delete all the elements of/>invoking collection except the specified collection

6 public int size()

It return the total number
of elements in thecollection

7 public void clear()

It removes the total no o
f element from thecollection

8 public boolean contains(object element)

It is used
;to search an element

9 public boolean containsAll(Collection c)

It is used&nbs
p;to search the specified/>collection in this collection

10 public Iterator iterator()

It returns an iterator

11 public Object[] toArray()

It converts collection into&
nbsp;array

12 public boolean isEmpty()

It checks if collection
is empty

13 public boolean equals(Object element)

It matches two&n
bsp;collection

14 public int hashCode()

It returns the hashcode num
ber forcollection

Question: What is Iterator interface?

Answer: Iterator interface provides the facility of iterating the el
ements in forward direction only

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