title: What is the most efficient Java Collections library?
body: <p>What is the most efficient Java Collections library?</p>
  
  <p>A few years ago, I did a lot of Java and had the impression back then that <a href="http://trove4j.sourceforge.net/" rel="noreferrer">trove</a> is the best (most efficient) Java Collections implementation. But when I read the answers to the question "<a href="https://stackoverflow.com/questions/130095/most-useful-free-java-libraries">Most useful free Java libraries?</a>" I noticed that <a href="http://trove4j.sourceforge.net/" rel="noreferrer">trove</a> is hardly mentioned. So which Java Collections library is best now? </p>
  
  <p><strong>UPDATE:</strong> To clarify, I mostly want to know what library to use when I have to store millions of entries in a hash table etc. (need a small runtime and memory footprint).</p>