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Collection

aakash bhatt
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Joined: Jan 09, 2003
Posts: 182
How do i read the 1st and the last value from the Collection

Regards,
aakash
Stan James
(instanceof Sidekick)
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Joined: Jan 29, 2003
Posts: 8791
Have you explored the JavaDoc for collection? See if that helps you find a couple ways.


A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
A Kumar
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Joined: Jul 04, 2004
Posts: 979
Associate an iterator to the collection and get the first and the last elements in the collection..

U may need to typecast the object when retrieving the element

bye
aakash bhatt
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Joined: Jan 09, 2003
Posts: 182
I have got iterator but it would iterate one by one. I do not want to write a while loop and break statement for 1st element
and for last element to iterate the whole collection through iterator has next.

Is there any other way, as Collectio have size() but do not have any get method to retrieve the element.
Any other way around other than this.

Thanks
Stan James
(instanceof Sidekick)
Ranch Hand

Joined: Jan 29, 2003
Posts: 8791
The loop is one choice, toArray might be another. I wouldn't worry much about the efficiency of the loop unless you have bazillions of entries. Collection doesn't have item(n) or elementAt(n). Some of the implementing classes do, but if you have to work with Collection you can only use Collection methods.
David Harkness
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Joined: Aug 07, 2003
Posts: 1646
If you have to write this against a Collection rather than List, you have no choice but to iterate (toArray will iterate and allocate an array, so it's possibly more expensive [ArrayList has an array already, so it can use System.arraycopy(), so it won't iterate, but I digress]).

The reason is that Collection is the lowest common denominator of a "thing that holds other objects," and it has no concept of ordering. List provides indexed access, allowing you to call list.get(0) and list.get(list.size()-1).

Note that this implies that Collection itself doesn't have any idea of "first" and "last" elements. In fact, it's conceivable (though unlikely in practice) that getting the first and last elements from a generic Collection could return different elements on subsequent calls.

For example, if I'm holding five coins in my hand, which one is the first one? And after I shake them around in my hand? The collection of coins hasn't changed since they are unordered.

Are you sure you don't have a List?
 
Don't get me started about those stupid light bulbs.
 
subject: Collection