title: Using Guava Cache As Map with Time Based Eviction
body: <p>I basically need a map where entries would expire after a specific known time period and then are removed.
  The way it's being used in my app is not really a cache but it seems Guava cache can serve the purpose. Would this be the right choice? One thing is I'm going to need to query if the map is empty and I saw that Guava has only a <code>size</code> function which its documentation says is only an approximation.</p>