title: How to delete an item from a Set?
body: <pre><code>final Set&lt;Expression&gt; exps = meng.getExps();
  Iterator&lt;Expression&gt; iterator = exps.iterator();
  final Expression displayedExp = exps.iterator().next();
  exps.remove(displayedExp);
  </code></pre>
  
  <p>This code would return the following run-time exceptions trace:</p>
  
  <pre><code>null
  java.lang.UnsupportedOperationException
          at java.util.Collections$UnmodifiableCollection.remove(Collections.java:1021)
  </code></pre>
  
  <p>The Set implementation of meng.getExps() is a LinkedHashSet.</p>