Index.jsp
<form method="post" action="serv">
Enter Latest Reading <input type="text" name="t1"> <br>
Enter Previous Reading <input type="text" name="t2"> <br>
<input type="submit" value="SEND">  
</form>
LoginServlet.java
@WebServlet("/serv")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    PrintWriter out = res.getWriter();   
    out.println("<u>Following are your Bill Particulars</u><br><br>");   
    req.setAttribute("unitRate", new Double(8.75));
    req.getRequestDispatcher("/Test").include(req, res); 
    out.println("<br><br>Please pay the bill amount before 5th of every month to avoid penalty and disconnection");   
    out.close();
    }
}
IncludeServlet.java
@WebServlet("/Test")
public class IncludeServlet extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
        PrintWriter out = res.getWriter();   
        int latestReading = Integer.parseInt(req.getParameter("t1"));   
        int previousReading = Integer.parseInt(req.getParameter("t2"));   
        Object obj = req.getAttribute("unitRate");
        Double d1 = (Double) obj; 
        double rate = d1.doubleValue();   
        int noOfUnits = latestReading-previousReading; 
        double amountPayable = noOfUnits * rate;   
        out.println("Previous reading: " + previousReading); out.println("<br>Current reading: " + latestReading); 
        out.println("<br>Bill Amount Rs." + amountPayable); 
    }
}
When I run the above project, only the response of LoginServlet is displayed in a browser, I'm unable to include the response of IncludeServlet.java.
All System.out.println("") of LoginServlet is being display is console only, non from IncludeServlet.
I also use debugger, but this is not going into IncludeServlet.java page.
                        
In your
IncludeServletinstead of overridingdoGetmethod overridedoPost, Since Post request is coming fromHTMLUpdate: Also write
res.setContentType("text/html");in both servlet so that your html written inout.printexecutes otherwise your output will look like<br><br>Please pay the bill amount before 5th of every month to avoid penalty and disconnection.