validate that a radio button was chosen struts2

[Jordan Smith]

hi!

i iterate over collection of question and answers.

<s:iterator value="videoQuestion" status="pos" id="p">
		<s:property value="%{#pos.count}" />. <s:property value="content" />
		<s:radio name="answer[%{id}]" list="answers" listKey="id" listValue="content" />
		<br /><br />
	</s:iterator>

    

how can i validate that all the questions were answered?

I hold the result in List<String> answer;

thanks!