example15_6.java

java jdbc中的部分可以运行的源代码

import java.sql.*;
import java.util.LinkedList;
public class example15_6
{
	public static void main(String args[])
	{
		Connection con;
		Statement sql;
		ResultSet rs;
		LinkedList list=new LinkedList();
		try
		{
			Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
		}
		catch(ClassNotFoundException e)
		{
			System.out.println(""+e);
		}
		try
		{
			con=DriverManager.getConnection("jdbc:odbc:mmm","mcx","123");
			sql=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);
			rs=sql.executeQuery("SELECT * FROM stu ");
			rs.last();

			int lownum=rs.getRow();
			int num=lownum;
			for(int i=1;i<=num;i++)
			{list.add(new Integer(i));}
			double sum=0;
			int k=3;
			int numk=k;
			while(k>0)
			{
				int i=(int)(Math.random()*list.size());
				int index=((Integer)list.get(i)).intValue();
				rs.absolute(index);
				int number=rs.getInt(1);
				String name=rs.getString(2);
				String course=rs.getString("course");
				int score=rs.getInt("score");
				System.out.println("学号"+number);
				System.out.println("姓名"+name);
				System.out.println("成绩"+score);
			    System.out.println("课程"+course);
			    sum=sum+score;
			    k--;
			    list.remove(i);

			}
			System.out.println("numk average score"+sum/numk);
			/*rs.afterLast();
			while(rs.previous())
			{
			  int number=rs.getInt(1);
			  String name=rs.getString(2);
			  String course=rs.getString("course");
			  int score=rs.getInt("score");
			  System.out.println("学号"+number);
			  System.out.println("姓名"+name);
			  System.out.println("成绩"+score);
			  System.out.println("课程"+course);
			}
			System.out.println("output the second record");
			rs.absolute(2);
			int number2=rs.getInt(1);
		    String name2=rs.getString(2);
			String course2=rs.getString("course");
			int score2=rs.getInt("score");
			System.out.println("学号"+number2);
			System.out.println("姓名"+name2);
			System.out.println("成绩"+score2);
			System.out.println("课程"+course2);*/
			con.close();
		}
		catch(SQLException e)
		{System.out.println(e);}
	}

}