Core Java - Array List Collections

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Array List Collections

What is Use of declaring an array list object like
List list = new ArrayList() rather than creating object like ArrayList arr = new ArrayList();

Total Answers and Comments: 6

Last Update: July 13, 2009 Asked by: rgmanoj

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Best Rated Answer

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Submitted by: rariedel

In the simple example given, there is no particular advantage; however, in many situations it is often useful to interact with the derived class using only the interface contract from which is was derived.

Using constructs of this type are useful when it is not known in advance which of its many potential derived class implementations will be actually be instantiated. This allows generic programming constructs to be applied to a plethora of potential run-time variations.

Above answer was rated as good by the following members:
sandeep549, deepkrisna

May 23, 2008 15:18:54

rariedel

Member Since: May 2008 Contribution: 8

RE: Array List Collections

In the simple example given there is no particular advantage; however in many situations it is often useful to interact with the derived class using only the interface contract from which is was derived.

Using constructs of this type are useful when it is not known in advance which of its many potential derived class implementations will be actually be instantiated. This allows generic programming constructs to be applied to a plethora of potential run-time variations.

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May 26, 2008 06:14:34

zizou

Member Since: May 2008 Contribution: 2

RE: Array List Collections

Hi
this technique is much more advantageuous as it'easy to cast the created object in runtime easily to another subclass of the list super classs.

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June 15, 2008 17:07:30

interviewprep9

Member Since: June 2008 Contribution: 10

RE: Array List Collections

Can someone please explian more eloborately on this one? Using List list new ArrayList() will I be invoking list's methods or the ArrayList methods with the reference variable list

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June 27, 2008 05:35:11

manjot.kr

Member Since: June 2008 Contribution: 1

RE: Array List Collections

List is an interface where as Arraylist is a class.
Arraylist implements all the methods in List...
So the arraylist's methods are invoked as the method body is present in Arralist

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July 05, 2008 06:37:58

R.Raj

Member Since: April 2008 Contribution: 3

RE: Array List Collections

Yes It is possible to invoke the methods of ArrayList using the reference variable list.
Infact it is used for that purpose only.

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July 11, 2009 09:05:04

shailesh.pandit

Member Since: July 2009 Contribution: 1

RE: Array List Collections

We may decide later to use the LinkedList instead of ArrayList in this situation we just need to replace the new ArrayList() part with new LinkedList() if we keep the referance variable as List interface.

whereas if we keep ArrayList as the referance variable it will be cumbersome.

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