title: The Guava library: What are its most useful and/or hidden features?
body: <p>I have had a quick scan of the <a href="https://google.github.io/guava/releases/snapshot/api/docs/" rel="noreferrer">Guava API</a> and the new collection types it provides(<code>Multimap</code> and <code>BiMap</code> for example appear useful) and I am thinking of including the library in the project(s) I work on.</p>
  
  <p>However, I also have a reticence to include libraries willy-nilly if they are of no great benefit and learning the features wastes valuable time.</p>
  
  <p>Have you included the Guava library in your project and has it proved useful in any unexpected way? Would you always use it in the future? What has been its main benefit/time saver? What are its hidden features?</p>