GetSession

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class GetSession extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
    HttpSession hs=request.getSession();
    String str1=(String)hs.getAttribute("a");
    String str2=(String)hs.getAttribute("b");
    out.println(str1+str2);
    }
}

SetSession

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class SetSession extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws IOException, ServletException
    {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
    HttpSession hs=request.getSession();
    hs.setAttribute("a","pakistan");
    hs.setAttribute("b","india");
    out.println("Done");
    }
}