Re: Merging Linked Lists

"Daniel Pitts" <>
19 Dec 2006 15:49:23 -0800
Damo wrote:

Daniel Pitts wrote:

Is there any reason not to use a Set instead?

Ye, I was just reading about Sets , there and the more I read the more
inclined I am to use them. How are they as regards efficiency as
opposed to linked lists? Efficiency is my main prioity for this project.

Well, it certainly depends on what your using them for. However,
efficiency should NEVER be the main priority of any project. Creating
something that WORKS should be the main priority.
You need to make something that works and is easy to read. After that,
if it runs to slowly, you can run it through a profiler and figure out
what parts of it are taking the most amount of time. You'd often be

If you start with something that works and is easy to maintain, then
tweaking the speed will be a lot easier. If you worry about it too
soon (its called premature optimization), then you might end up with a
very slow program anyway, but it would be harder to optimize the RIGHT
In any case:
HashSets are often more effecient when adding and removing arbitrary
elements if you need to ensure uniqueness. They are of comparable
speed when iterating through the contained values.
ArrayLists are generally faster than LinkedLists if you only add/remove
from the end of the list, but look up arbitrary elements in the middle
of the list.

If you need to maintain order, then look into LinkedHashSet.
While it has a little more overhead than HashSet, it can be faster when
iterating over the entire set.

So. My professional suggestion is to make all of your types "Set" (or
"Collection" is better, depending on what you need to do), and
instantiate with "new HashSet()". If you find, once you finish the
working project, that the HashSet is too slow for one reason or
another, it will be easy to modify your code to use a different type of
Collection, better suited to your domain.

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