如何把数据库里面的一列求和，然后把结果取出来显示在jsp页面上？

怎么把数据库里面的一列求和，然后把结果取出来显示在jsp页面上？？
我是新手啊，我把数据里的数据全取出来放在ArrayList里面了，但是我想让km（数据库第十列）这一列的数求和，然后把结果显示在jsp页面上，该怎么做？jsp页面上怎么接收？拜求各位大神帮忙指导啊。我具体的servlet代码如下
package bao;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class Insert extends HttpServlet {
private static final long serialVersionUID = 1L;
    public static final String DBURL="jdbc:mysql://localhost:3306/test";
    public static final String DBUSER="root";
    public static final String DBPASS="";
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Insert() {
        super();
        // TODO Auto-generated constructor stub
    }

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
} 

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        request.setCharacterEncoding("UTF8") ;
        response.setCharacterEncoding("utf-8") ;
        String day=request.getParameter("day");
        String classt=request.getParameter("classt");
        String starttingtime1=request.getParameter("starttingtime");
        int starttingtime=Integer.parseInt(starttingtime1);
        String finishtime1=request.getParameter("finishtime");
        int finishtime=Integer.parseInt(finishtime1);
        String origin=request.getParameter("origin");
        String finish=request.getParameter("finish");
        String startkm1=request.getParameter("startkm");
        int startkm=Integer.parseInt(startkm1);
        String finishkm1=request.getParameter("finishkm");
        int finishkm =Integer.parseInt(finishkm1);
        int km;       
        int allowance=0;
        km=finishkm-startkm;

        try{
         Connection conn=null;
         Statement st=null;
         Class.forName("com.mysql.jdbc.Driver");
         conn =DriverManager.getConnection("jdbc:mysql://localhost:3306/test?user=root&password=&useUnicode=true&characterEncoding=utf-8");
         st =conn.createStatement();
         String sql="insert into jixiao2(day,classt,starttingtime,finishtime,origin,finish,startkm,finishkm,km,allowance)"+"values('"+day+"', '"+classt+"', '"+starttingtime+"', '"+finishtime+"','"+origin+"','"+finish+"', '"+startkm+"','"+finishkm+"','"+km+"','"+allowance+"')";
         st.execute(sql);

        
        } catch (Exception e)
        {
         e.printStackTrace();
        }
        try
    {
     Class.forName("com.mysql.jdbc.Driver");
     Connection conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS);
     ArrayList<Jixiao> list =new ArrayList<Jixiao>();
     String sql ="select * from jixiao2";
//      String sql1="select sum(km) as sumkm from jixiao2";