I believe, inadvertently you have used a construct that makes it work.
<%@ page language="java" import="java.util.*" %>
<HTML>
<HEAD>
<TITLE>A JSP USEBEAN APPLICATION</TITLE>
</HEAD>
<BODY BGCOLOR="white">
<jsp:useBean id="col"
scope="session" class="java.util.ArrayList" type="Collection"/>
Class Name = <%= col.getClass().getName() %>
</BODY>
</HTML>
This only works because of the import="java.util.*". Remove that and you will see that it will stop working.
Reason: In
Tomcat the equivalent JSP is translated to
...
import java.util.*;
...
col = (Collection) _jspx_page_context.getAttribute("col", PageContext.SESSION_SCOPE);
