When you say 'swap a table for another without reloading', if you mean dynamically change the contents of an HTML table, then it can be done with DHTML. This is NOT a PHP thing as PHP will work on the file server side (requiring a reload). You could use an embedded IFRAME that posts to your server (appears not to reload, but actaully does).
http://msdn.microsoft.com and http://devedge.netscape.com/ are good sites to read up from and get the DHTML information on how to update HTML client side.
My point, if I understand what you want correctly, a java applet is not neccesary to accomplish this.