multiple selected values

[Billy Ng]

I have a html:select that enabled multiple attribute.

             <html:select property="collectionSelect" size="10" multiple="true">
              <html:options collection="classOptions" property="value" 
labelProperty="label"/>
             </html:select>

I know I can use the <html:select>'s value attribute to mark a pre-selected item.  But 
if I have more than 1 item to be selected, what variable should I pass to the value 
attribute?

Thanks in advance!

Billy Ng