📄 example5_4.jsp
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<%@page contentType="text/html;charset=gb2312" %>
<%@page import="java.sql.*" %>
<%@page import="java.util.*" %>
<html>
<body>
<%
Vector vector=new Vector();
Connection con;
Statement sql;
ResultSet rs;
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcdriver");
}catch(ClassNotFoundException e){
}
try{
con=DriverManager.getConnection("jdbc:odbc:pubs","","");
sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs=sql.executeQuery("select * from students");
out.print("<Table Border>");
out.print("<tr>");
out.print("<TH width=100>"+"学号");
out.print("<TH width=100>"+"姓名");
out.print("<TH width=50>"+"数学");
out.print("</tr>");
rs.last();
int lownumber=rs.getRow();
int number=lownumber;
for(int i=1;i<=number;i++)
vector.add(new Integer(i));
double sum=0;
int 抽取数目=4;
int k=抽取数目;
while(抽取数目>0){
int i=(int)(Math.random()*vector.size());
int index=((Integer)vector.elementAt(i)).intValue();
rs.absolute(index);
out.print("<tr>");
out.print("<td>"+rs.getString(1)+"</td>");
out.print("<td>"+rs.getString(2)+"</td>");
int math=rs.getInt("数学成绩");
out.print("<td>"+math+"</td>");
out.print("</tr>");
sum=sum+math;
抽取数目--;
vector.removeElementAt(i);
}
out.print("</Table>");
out.print("平均成绩是："+sum/k);
con.close();
}catch(SQLException ee){
}
%>
</body>
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