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    <p>Unboxing is fast - no allocations are required. Boxing is a potentially slower, as it needs to allocate a new object (unless it uses a pooled one).</p> <p>Are you sure you've really got a problem though? Don't complicate your code until you've actually proved that this is a significant hit. I very much doubt that it is.</p> <p>There are collection libraries available for primitive types, but I would stick to the normal HashMap from the JRE until you've profiled and checked that this is causing a problem. If it really only is <em>thousands</em> of lookups, I very much doubt it'll be a problem at all. Likewise if you're lookup-based rather than addition-based (i.e. you fetch more often than you add) then the boxing cost won't be particularly significant, just unboxing, which is cheap.</p> <p>I would suggest using <code>intValue()</code> rather than the cast to convert the value to an <code>int</code> though - it makes it clearer (IMO) what's going on.</p> <p>EDIT: To answer the question in the comment, <code>HashMap.get(key)</code> will be faster than <code>ArrayList.indexOf(key)</code> <em>when the collection is large enough</em>. If you've actually only got five items, the list may well be faster. I assume that's not really the case though.</p> <p>If you really, really don't want the boxing/unboxing, try <a href="http://trove4j.sourceforge.net/" rel="nofollow noreferrer">Trove</a> (TObjectHashMap). There's also <a href="http://acs.lbl.gov/~hoschek/colt/" rel="nofollow noreferrer">COLT</a> to consider, but I couldn't find the right type in there.</p>
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    1. USFabian Steeg
    1. USJon Skeet
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    1. COLeave it to Jon Skeet to give an answer that makes the whole question irrelevant...
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      1. USMichael Myers
    2. COLooks like benchmarking is going to be the only way to test this properly. I wasn't aware that unboxing is cheap. I'll have to do some profiling to spot the bottle necks. That said, based on the internals of the 2 which should be quicker ArrayList<String>.indexOf or HashMap<String, Integer>.get
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      1. USAdrian Hope-Bailie
    3. COSorry, one more comment. It IS a significant hit. I need every microsecond I can get here :)
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