i put TestServlet into the folder as follows:
..webapps\star\WEB-INF\classes\com\stardeveloper\servlets


then add the following line in the server.xml in /conf:
<Context path="/star" docBase="star" debug="1" reloadable="true"/> before the "</Host></Engine></Service>"

i will be crazy due to this problem. could you please help me ?

Ue, all I can say is to reread this updated tutorial. The solution to your problem is described in detail in this updated tutorial. You now don't need to add anything in the server.xml file. You now do need to add Servlet specific tags in the web.xml file to deploy it so that you can access it using URL like /TestServlet.