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POFastest Java HashSet<Integer> library
 

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    <p>In addition to <a href="https://stackoverflow.com/questions/629804/what-is-the-most-efficient-java-collections-library">this quite old post</a>, I need something that will use primitives and give a speedup for an application that contains lots of <code>HashSet</code>s of <code>Integers</code>:</p> <pre><code>Set&lt;Integer&gt; set = new HashSet&lt;Integer&gt;(); </code></pre> <p>So people mention libraries like Guava, Javalution, Trove, but there is no perfect comparison of those in terms of benchmarks and performance results, or at least good answer coming from good experience. From what I see many recommend Trove's <code>TIntHashSet</code>, but others say it is not that good; some say Guava is supercool and manageable, but I do not need beauty and maintainability, only time execution, so Python's style Guava goes home :) Javalution? I've visited the website, seems too old for me and thus wacky.</p> <p>The library should provide the best achievable time, memory does not matter.</p> <p>Looking at "Thinking in Java", there is an idea of creating custom <code>HashMap</code> with <code>int[]</code> as keys. So I would like to see something similar with a <code>HashSet</code> or simply download and use an amazing library.</p> <p><strong>EDIT</strong> (in response to the comments below) So in my project I start from about 50 <code>HashSet&lt;Integer&gt;</code> collections, then I call a function about 1000 times that inside creates up to 10 <code>HashSet&lt;Integer&gt;</code> collections. If I change initial parameters, the numbers may grow up exponentially. I only use <code>add()</code>, <code>contains()</code> and <code>clear()</code> methods on those collections, that is why they were chosen.</p> <p>Now I'm going to find a library that implements <code>HashSet</code> or something similar, but will do that faster due to autoboxing <code>Integer</code> overhead and maybe something else which I do not know. In fact, I'm using ints as my data comes in and store them in those <code>HashSet</code>s.</p>
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    1. USSophie Sperner
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    1. COIf memory truly doesn't matter at all, I'd suggest a BitSet (with an offset, if you need to handle negative numbers).
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      1. USTed Hopp
    2. COYou haven't given enough information. What is your use case that you have to squeeze out the last 1% improvement? Are the integers evenly distributed in `[Integer.MIN_VALUE, Integer.MAX_VALUE]`? Performance will depend on distribution, the hash function, and memory allocated. What do you mean by "lots of HashSets"... Do the "lots of HashSets" participate in their own higher-level data structure? Please flesh out the question.
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      1. USJim Garrison
    3. COWe don't know enough about your project to make this call for you. Most projects can use `Set<Integer>` without any issues. I would suggest you try out the libraries you mentioned and measure your performance.
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      1. USJeffrey
 

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