checkboxlist展示，value裏的值指定默認選中哦：
<body>
<p:checkboxlist
name="checkboxlist"
label="list1"
list="{'Java','C++','C#'}"
value="{'Java'}"
></p:checkboxlist>
<hr/>
</body>
doubleselect展示：
<p:form action="city">
<p:set name="fool"
value="#{'河南':{'焦作','鄭州','濟源 '},'浙江':{'杭州','台州','寧波','溫州'}}"
></p:set>
<p:doubleselect doubleList="#fool[top]"
list="#fool.keySet()"
doubleName="technology"
label="technology"></p:doubleselect>
</p:form>