jdbc---查询语句的使用（executeQuery）

package com.syy;

import domain.student;

import java.sql.*;
import java.util.ArrayList;

public class JdbcDemo3 {

    public static void main(String[] args)throws Exception {
        ArrayList<student> stu = getstudent();
        for (student stu1 : stu) {
            System.out.println(stu1);
        }

    }

    private static ArrayList<student> getstudent() throws SQLException {
        ArrayList<student> array = new ArrayList<student>();
        Connection con = null;
        Statement stat = null;
        ResultSet resultSet=null;
        try {
            //1、加载驱动类
            Class.forName("com.mysql.jdbc.Driver");
            //2、与数据库建立连接
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db4", "root", "1234");
            //3、获取sql语句对象
            stat = con.createStatement();
            //4、定义sql语句
            String sql = "select *from student ";
            //通过executeQuery返回结果集
             resultSet = stat.executeQuery(sql);
            //判断是否有下一个数据---获取下一个元素
//        resultSet.next();相当于指针下移
            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String grade = resultSet.getString("grade");
                System.out.println(id + "\t" + name + "\t" + grade);
                //把字段封装成对象
                //创建对象
                student s = new student();
                s.setId(id);
                s.setName(name);
                s.setGrade(grade);
                //把对象添加到集合中
                array.add(s);

            }


        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (con != null) {
                con.close();
                con = null;
            }
            if (stat != null) {
                    stat.close();
                    stat = null;
                }
            if (resultSet!=null){
                resultSet.close();

            }

            }

        return array;
    }

}