测试oracle连接出现的小疑点，纠结了半天没找出，汗

package com.niit.dao;
 
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
 
import com.niit.entity.Student;
import com.niit.iface.IStuDao;
 
public class StudentDao extends BaseDao implements IStuDao
{
    private Connection con;
    private ResultSet rs;
    private PreparedStatement pstmt;
 
    public ArrayList<Student> findAllStudent()
    {
        ArrayList<Student> stuList=new ArrayList<Student>();
         
        con=getConnection();
 
        if(con!=null)
        {
            try
            {
                pstmt=con.prepareStatement("select * from student");
                 
                rs=pstmt.executeQuery();
                //此处为false,但是上面的sql语句在oracle中能查到,为啥这里查不到呢
                System.out.println(rs.next());
 
                while(rs.next())
                {
                    Student stu=new Student();
                     
                    stu.setStuName(rs.getString(1));
                    stu.setStuId(rs.getInt(2));
                    stu.setBirthday(rs.getTimestamp(3));
                    stu.setSex(rs.getString(4));
                    stu.setEmail(rs.getString(5));
                     
                    stuList.add(stu);    
                }
                 
            } catch (SQLException e)
            {