<zk>
  <zscript>
    ListModelList model = new ListModelList(Collections.nCopies(250000,"item"));
  </zscript>
  
  <listbox width="200px" height="540px" model="${model}">
    <custom-attributes org.zkoss.zul.listbox.rod="true"/>
    <listhead>
     <listheader label="Load On Demand" sort="auto" />
    </listhead>
  </listbox>
</zk>