Java Script Program

<%-- Document : index Created on : Oct 15, 2012, 9:21:34 PM Author : SAMSUNG --%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>

    <form method="get">

        Enter First Integer<input type="text" name="t1" value="" />
        Enter Second Integer<input type="text" name="t2" value="" />
        <input type="submit" value="Submit" name="b1" />

    </form>
    <%
    int i=Integer.parseInt(request.getParameter("t1"));
    int j=Integer.parseInt(request.getParameter("t2"));
    int k=i+j;
    System.out.println("Total="+k);
    %>                     

</body>

I Am Writing THis COde It Is GIving The Following Error

Exception report

message

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

exception

org.apache.jasper.JasperException: java.lang.NumberFormatException: null root cause

java.lang.NumberFormatException: null note The full stack traces of the exception and its root causes are available in the Sun Java System Application Server 9.1 logs.

Sun Java System Application Server 9.1

Where Is The Problem? Please Help