title: Java nio WatchService for multiple directories
body: <p>I want to watch (monitor) multiple directories using Java NIO  <a href="https://docs.oracle.com/javase/7/docs/api/java/nio/file/WatchService.html" rel="noreferrer"><code>WatchService</code></a>.
  My problem here is the number of directories to watch is dynamic and the user can add any number of directories to the <code>WatchService</code>. Is this achievable?</p>