codice:
type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

org.apache.jasper.JasperException: Exception in JSP: /Nuovo.jsp:43

40:        
41:    <select id="Argomento" name= "Argomento" >
42:    <%
43:    for(int i=0;i<lista.size();i=i++){ 
44:       Argomento arg = (Argomento) lista.get(i);
45:    %>
46:           <option value="<%= arg.getId() %>">


Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:467)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:389)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	provaprogetto.Login.doGet(Login.java:83)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


root cause 

java.lang.NullPointerException
	org.apache.jsp.Nuovo_jsp._jspService(Nuovo_jsp.java:88)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	provaprogetto.Login.doGet(Login.java:83)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:803)


note The full stack trace of the root cause is available in the Apache Tomcat/5.5.23 logs.