public class Userdao extends BaseDao{
    //查询名字
    public ArrayList<Student> allName(){
        ArrayList<Student> allname = new ArrayList<Student>();
        String sql = "select sname from student";
        try {
            super.getConnection();
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while(rs.next()){？？？？？？？？？？？？？？？？？？？？这是什么意思
                Student st = new Student();
                st.setSid(rs.getInt("sid"));？？？？？？？？？？？？
                st.setSname(rs.getString("sname"));？？？？？？？？？？？
                st.setSsex(rs.getString("ssex"));？？？？？？？？？？
                allname.add(st);
               
            }
            try {
                super.closeAll();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return allname;
        
    }