title: freemarker.template.TemplateException: Expected hash
body: <p>I am trying to generate a Freemarker template, but I get:</p>
  
  <pre><code>freemarker.template.TemplateException: Expected hash. ul evaluated instead to
      freemarker.template.SimpleSequence on line 105, column 40
      in Freemarker/MUC/UnitIndex.ftl.
  </code></pre>
  
  <p>My class:</p>
  
  <pre><code>public class UnitLists extends TreeSet&lt;UnitList&gt;
  ...
  </code></pre>
  
  <p>added to param as following:</p>
  
  <pre><code>params.put("unitLists", this.unitLists);
  ...
  </code></pre>
  
  <p>used in the template:</p>
  
  <pre><code>&lt;#list unitLists as ul&gt;
      &lt;a href="${ul.linkFromRoot}" class="mya2"&gt;${ul.tag}&lt;/a&gt;
  &lt;/#list&gt;    
  </code></pre>
  
  <p>What am I doing wrong?</p>