请教一个数据输出的问题，麻烦大家帮忙看看！！

问题：IO输出多个字段，取的三张表的字段也不一样，1.如何在输出的文件表中添加String类型的相应组长的字段？？？要求要和表1、表2、表3的字段相对应！！！
2.如何先先输出第一行标题，然后再循环输出表的内容？？3.如何添加一列字段计算合计:（业务量*单价）？？4.怎样将null值显示为没有值？？输出为：
组长 业务量 单价 员工编号 经理 地区 合计
组长1 A B C null null A*B
.... .. ... ... ... ... ...
组长2 D E F null G D*E
.... ... .. .. ... ... ...
组长3 H I J K null H*I
.... .. .. ... ... ... ...

import java.sql.*;

import java.util.*;

import java.io.*;



public class test extends ClassObj{

public static void main(String[] args) throws Exception {

        try {

            ArrayList<ClassObj> lst = test.getResultLst();

            String contents = test.formatLst(lst);

            String fileName = "C:\\result.txt";

            test.saveFile(fileName, contents);

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

  static ArrayList<ClassObj> getResultLst() throws Exception {

        String url = "jdbc:odbc:study";

        String user = "sa";

        String password = "123";

ArrayList <ClassObj> lst = new ArrayList <ClassObj>();

        Connection con = null;

        Connection con2 = null;

        Connection con3 = null;

        PreparedStatement pstmt = null;

        

        ResultSet rs = null;

        ResultSet rs2 = null;

        ResultSet rs3 = null;

        String sql = "select 业务量 as A,单价 as B,员工编号 as C from 表1";

        String sql2 = "select 业务量 as D,单价 as E,员工编号 as F,地区 as G from 表2";

        String sql3 = "select 业务量 as H,单价 as I,员工编号 as J,经理 as K from 表3";

        try{

            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

            con = DriverManager.getConnection(url,user,password);



            pstmt = con.prepareStatement(sql);

            pstmt2 = con.prepareStatement(sql2);

            pstmt3 = con.prepareStatement(sql3);

            rs = pstmt.executeQuery();

            rs2 = pstmt2.executeQuery();

            rs3 = pstmt3.executeQuery();

          String fa = "组长1";

          String fb = "组长2"；

          String fc = "组长3"；

          

          ClassObj c1=null;

          while(rs.next()){               //怎样将fa,fb,fc跟相应的rs，rs2，rs3对应循环输出。

              c1=new ClassObj();            //c1.setBand(rs.getString("fa"));?????

              c1.setBuss(rs.getDouble("A"));

              c1.setPrice(rs.getDouble("B"));

              c1.setId(rs.getString("C"));

                                             //怎么才能计算合并输出????

                                            //c1.setId(rs.getDouble(A*B));

              lst.add(c1);

          }

          while(rs2.next()){

              c1=new ClassObj();

              c1.setBuss(rs.getDouble("D"));

              c1.setPrice(rs.getDouble("E"));

              c1.setId(rs.getString("F"));

              c1.setLand(rs.getString("G"));

              lst.add(c1);

          }

          while(rs3.next()){

              c1=new ClassObj();

              c1.setBuss(rs.getDouble("H"));

              c1.setPrice(rs.getDouble("I"));

              c1.setId(rs.getString("J"));

              c1.setMan(rs.getString("K"));

              lst.add(c1);

          }



        }catch(Exception e){

            e.printStackTrace();

        }finally{

            try{

                if (rs != null)

                    rs.close();

                if (pstmt != null)

                    pstmt.close(); 

                if (con != null)

                    con.close();

                

            }catch(Exception e){}

        }

      }

static void saveFile(String fileName, String contents) 

throws IOException { 

File f = new File(fileName); 



if (f.exists()){ 

throw new IOException("file exists..."); 

} 

if (!f.createNewFile()) { 

throw new IOException("file create failure..."); 

} 



try { 

BufferedWriter output = new BufferedWriter(new FileWriter(f)); 

output.write(contents); 

output.close(); 

} catch (Exception e) { 

throw new IOException(e); 

} 

} 



static String formatLst(ArrayList <ClassObj> lst){ 

String contents = "";                   //如何在这先循环第一行标题？？

for(int i=0;i <lst.size();i++){ 

contents +=lst.get(i).getBand+"\t"+lst.get(i).getBuss+"\t"+lst.get(i).getPrice+"\t"+lst.get(i).getId+"\t"+lst.get(i).getLand+lst.get(i).getMan+"\t"+lst.get(i).getSum+"\n"; 

} 

return contents; 

} 

}

class ClassObj {

    private String Band;



    private Double Buss;



    private Double Price;

    

    private String Id;

    

    private String Land;

    

    private String Man;

   

    private Double Sum;

    

//get..set

    public String toString() {

        return "ClassObj{classBand=" + this.classBand +",classId="

                + this.classId + ",classGroup="

                + this.classGroup + ",classSum="

                + this.classSum + ",classNo=" + this.classNo +"}";

    }

}