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copied!<p>This is a case of premature unoptimization :-). You should never do something because you think it will be better/faster/make you happier. </p> <p>ArrayList has extra overhead, if you have no need of the extra features of ArrayList then it is wasteful to use an ArrayList. </p> <p>Also for some of the things you can do with a List there is the Arrays class, which means that the ArrayList provided more functionality than Arrays is less true. Now using those might be slower than using an ArrayList, but it would have to be profiled to be sure.</p> <p>You should never try to make something faster without being sure that it is slow to begin with... which would imply that you should go ahead and use ArrayList until you find out that they are a problem and slow the program down. However there should be common sense involved too - ArrayList has overhead, the overhead will be small but cumulative. It will not be easy to spot in a profiler, as all it is is a little overhead here, and a little overhead there. So common sense would say, unless you need the features of ArrayList you should not make use of it, unless you want to die by a thousands cuts (performance wise).</p> <p>For internal code, if you find that you do need to change from arrays to ArrayList the chance is pretty straight forward in most cases ([i] becomes get(i), that will be 99% of the changes).</p> <p>If you are using the for-each look (for( value : items) { }) then there is no code to change for that as well.</p> <p>Also, going with what you said:</p> <p>1) equal access speed, depending on your environment. For instance the Android VM doesn't inline methods (it is just a straight interpreter as far as I know) so the access on that will be much slower. There are other operations on an ArrayList that can cause slowdowns, depends on what you are doing, regardless of the VM (which could be faster with a stright array, again you would have to profile or examine the source to be sure).</p> <p>2) Wrappers increase the amount of memory being used.</p> <p>You should not worry about speed/memory before you profile something, on the other hand you shouldn't choose what you know to be a slower option unless you have a good reason to.</p>

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