例12-2.txt

这是一本java基础教程 对新手上路有很大帮助

import java.sql.*; 
import java.util.*;
public class Example12_2{
    public static void main(String args[]){
        ArrayList<Integer> list=new ArrayList<Integer>();
        Connection con;
        Statement sql; 
        ResultSet rs;
        try{  Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
        }
        catch(ClassNotFoundException e){}
        try {  con=DriverManager.getConnection("jdbc:odbc:hello","","");
              sql=con.createStatement               (ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
              rs=sql.executeQuery("SELECT * FROM message");
              rs.last();
              int lastNumber=rs.getRow();
              for(int i=1;i<=lastNumber;i++)
                    list.add(i);
              double sum=0;
              int samplingNumber=3;
              int count=samplingNumber;
              System.out.println("随机抽取"+count+"条记录:");
              while(samplingNumber>0){
                  int i=(int)(Math.random()*list.size());
                  int index=list.get(i);
                  rs.absolute(index);                   //游标移到这一行
                  String number=rs.getString(1);
                  String name=rs.getString(2);
                  java.sql.Date birth=rs.getDate(3);
                  double height=rs.getDouble("height");
                  System.out.println(number+","+name+","+birth+","+height);
                  sum=sum+height; 
                  samplingNumber--; 
                  list.remove(i);                      //list删除抽取过的元素
              }
              System.out.println(count+"条记录的平均身高："+sum/count);
              con.close();
        }
        catch(SQLException e1) {}
    }
}