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ArrayList does it maintain order

pendse anagha
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Joined: Mar 09, 2005
Posts: 44
Hello ,
I have a bunch of strings that I am getting in an arrayList
These are actually primary key field values of a certain table

I then go and get the value from the table and store it in another ArrayList
I return both the arrayLists to another program

My doubt / query is - will the arraylist maintain the order exactly as I have entered the data .

ArrayList keys = new ArrayList("1","2","3");
ArrayList vals= new ArrayList("cat","dog","rat");

So when I iterate over the secomd arrayList - "vals" will i always
get the values in the order - cat , dog , rat ?

If not - then could someone please suggest what I need to do ?

Thanks ,
-anagha
Ernest Friedman-Hill
author and iconoclast
Marshal

Joined: Jul 08, 2003
Posts: 24187
    
  34

Yes. A List, by definition, always preserves the order of the elements. This is true not only of ArrayList, but LinkedList, Vector, and any other class that implements the java.util.List interface.


[Jess in Action][AskingGoodQuestions]
K Riaz
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Joined: Jan 08, 2005
Posts: 375
You know, this could have been tested in 60 seconds (or less than the time it took to write the post) by just creating an ArrayList yourself, adding elements to it and then printing them out. You could then see if it was ordered.
miguel lisboa
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Joined: Feb 08, 2004
Posts: 1281
in case you'v java5 you can test this:

output:
a
b
c
0

EDIT:
i posted this before reading any answer
[ May 21, 2005: Message edited by: miguel lisboa ]

java amateur
Ernest Friedman-Hill
author and iconoclast
Marshal

Joined: Jul 08, 2003
Posts: 24187
    
  34

Originally posted by Kashif Riaz:
You know, this could have been tested ...


Well, yes, but you can't necessarily count on the results of this kind of test. You don't know if it's a quirk of the implementation, or if it's guaranteed behavior, until you read the documentation. From the javadocs:


An ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list.
pendse anagha
Ranch Hand

Joined: Mar 09, 2005
Posts: 44
Thanks ranchers - for the help
and yes Kashif - I did implement and check - believe me but just wanted some experts here to verify that my understanding was correct
- and as usual excellent people here are ready to help .

Thanks once again to all who have taken the trouble of helping me out

Regards ,
-anagha
David Keenan
Greenhorn

Joined: Dec 04, 2012
Posts: 2
what's the Jrebel link at the bottom all about? That's spam isn't it?
Jesper de Jong
Java Cowboy
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Joined: Aug 16, 2005
Posts: 14337
    
  22

Welcome to the Ranch David Keenan.

The link at the bottom for JRebel is not spam; it's just an advertisement.


Java Beginners FAQ - JavaRanch SCJP FAQ - The Java Tutorial - Java SE 8 API documentation
David Keenan
Greenhorn

Joined: Dec 04, 2012
Posts: 2
lol. thanks.
 
I agree. Here's the link: http://aspose.com/file-tools
 
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