Collections Interview Questions And Answers

What is Collection API?

It defines set of classes and interfaces which can be used for representing a group of objects as single entity
 

What is Collection framework?

It defines set of classes and inter faces which can be used for representing a group of objects as single entity
 

What  is difference between Collections and Collection?

Collection is an interface which can be used for representing a group of individual objects as single entity  and it acts as root interface of collection frame  work. Collections is an utility class to define several utility methods for Collection implemented class objects.
 

Explain about Collection interface?

  • This interface can be used to represent a group of objects as a single entity.
  • It acts as root interface for entire collection framework.
  • It defines the most commonly used methods which can be applicable for any collection implemented class object.


Explain about List interface?

List interface is a child interface of Collection interface. This can be used to represent group of individual objects in as a single entity where 

  • Duplicates are allowed
  • Insertion order is preserved


Explain about Set interface?

Set is a child interface of Collection interface. it can be used to represent a group of individual objects as a single entity where

  • Duplicate objects are not allowed.
  • Insertion order is not preserved


Explain about Map interface?

Remember it is not a child Interface of Collection Interface and hence Map and Collection Interfaces doesn’t have any relationship.

  • It can be used for representing a group of Objects as key, value pairs.
  • Both keys and values should be objects
  • Keys can t be duplicated but values can be duplicated.
  • it has  introduced in 1.2 version


Explain about ArrayList class?

ArrayList is a Collection which can be used to represent a group of objects as a single entity.

  • it is a implemented class for  List interface
  • Introduced in 1.2 version
  • The underlying data structure is resizable or growable array.
  • Insertion order is preserved 
  • Duplicates are allowed
  • Heterogeneous objects are allowed
  • null insertion is possible
  • This  class implements RandomAccess , Serializable , Cloneable interfaces
  • Best choice  for retrieval purpose and worst if our frequent operation is insertion or deletion in the middle.


What is RandomAccess Interface?

  • If a collection class implements RandomAccess interface then we can access any of its element with the same speed. 
  • RandomAccess interface is marker interface and it dosent contains any methods.
  • ArrayList and vector classes implements this interface.


Explain about LinkedList class?

LinkedList is a Collection implemented class which can be used for representing a group of objects as a single entity.

  • LinkedList is the implemetation class for List interface
  • Introduced in 1.2 version
  • Underlying data Structure is   DoubleLinkedList
  • Allows duplicates
  • Insertion order is preserved
  • Allows heterogeneous objects
  • null insertion is possible
  • LinkedList class implements Seriallizable and Cloneable interface but not RandomAccess interface
  • Best choice  if frequent operation is insertion or deletion an objects in middle  but worst choice if frequent operation is retrieval.

See also
Object Arrays and Collections

Do you have a Java Problem?
Ask It in The Java Forum

Java Books
Java Certification, Programming, JavaBean and Object Oriented Reference Books

Return to : Java Programming Hints and Tips

All the site contents are Copyright © www.erpgreat.com and the content authors. All rights reserved.
All product names are trademarks of their respective companies.
The site www.erpgreat.com is not affiliated with or endorsed by any company listed at this site.
Every effort is made to ensure the content integrity.  Information used on this site is at your own risk.
 The content on this site may not be reproduced or redistributed without the express written permission of
www.erpgreat.com or the content authors.