title: How to check value of Multimap is null or empty?
body: <p>I am using Multimap from Guava as shown below since I can have same keys many times but with different values.</p>
  
  <pre><code>Multimap&lt;Long, Plesk&gt; map = ArrayListMultimap.create();
  // populate data into map
  
  // extract value from the above map
  Collection&lt;Plesk&gt; plesk = map.get(id);
  </code></pre>
  
  <p>And now from the same multimap I am extracting a particular key value. Now how can I check whether <code>plesk</code> variable is null or not? After I print out my <code>map</code> variable, I see one entry as:</p>
  
  <pre><code>1100178=[null]
  </code></pre>
  
  <p>so <code>plesk</code> variable is getting value as <code>[null]</code> for id <code>1100178</code> and if I use below code to check for null and empty then it doesn't work:</p>
  
  <pre><code>if (CollectionUtils.isEmpty(plesk)) {
      // do stuff
  }
  </code></pre>
  
  <p>What is the right way to check whether value of multimap is null or not?</p>