title: Java Set<Set<String>> to String[][]
body: <p>How can I convert a <code>Set&lt;Set&lt;String&gt;&gt;</code> to a <code>String[][]</code>? I have tried <code>.toArray(new String[0])</code> but this doesn't seem to do the trick.</p>
  
  <p>Thanks!
  Christian</p>