title: Java List.add() UnsupportedOperationException
body: <p>I try to add objects to a <code>List&lt;String&gt;</code> instance but it throws an <code>UnsupportedOperationException</code>.
  Does anyone know why?</p>
  
  <p>My Java code:</p>
  
  <pre><code>String[] membersArray = request.getParameterValues('members');
  List&lt;String&gt; membersList = Arrays.asList(membersArray);
  
  for (String member : membersList) {
      Person person = Dao.findByName(member);
      List&lt;String&gt; seeAlso;
      seeAlso = person.getSeeAlso();
      if (!seeAlso.contains(groupDn)){
          seeAlso.add(groupDn);
          person.setSeeAlso(seeAlso);
      }
  }
  </code></pre>
  
  <p>The error message:</p>
  
  <pre>
  java.lang.UnsupportedOperationException
      java.util.AbstractList.add(Unknown Source)
      java.util.AbstractList.add(Unknown Source)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
  </pre>