一、说明

增 改 删是同一类
查询是另一类

二、增加和修改和删除

  /**
     * 支持增删改
     * @param sql
     */
    public void insert(String sql){
        Statement state= null;   //容器
        try {
            state = conn.createStatement();
//            String sql="insert into xs values('1108','张伟','汉企')";   //SQL语句
            state.executeUpdate(sql);         //将sql语句上传至数据库执行


        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            try {
                conn.close();//关闭通道
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

三、查询

    /**
     * 只支持查询
     * @param sql
     * @return
     */
    public List<String> query(String sql){
        Statement state= null;   //容器
        List<String> strings = new ArrayList<>();
        try {
            state = conn.createStatement();
            ResultSet resultSet = state.executeQuery(sql);
            while (resultSet.next()){
                String str = "";
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String password = resultSet.getString("password");
                String number = resultSet.getString("number");
                int sex = resultSet.getInt("sex");
                str = "id:"+id+" name:"+name+" password:"+password+" number:"+number+" sex:"+sex;
                strings.add(str);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return strings;
    }

四、测试类

package com.joychen1.jdbc;

import java.util.List;

public class Test {
    public static void main(String args[]){
        DBHelper dbHelper = new DBHelper();
        dbHelper.init();
//        String sql = "insert into users(name,password,sex,number)values('小小','654321',0,'00003')";
//       String sql = "delete from users where name='小小'";
//        String sql="update users set name='大大' where name='小小'";
        String sql ="select * from users";
        List<String> stringList = dbHelper.query(sql);
        for (String s:stringList){
            System.out.println(s);
        }
    }
}

DBHelper类中所有的代码如下

package com.joychen1.jdbc;

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

public class DBHelper {

    Connection conn;

    private String driverName="com.mysql.jdbc.Driver";
    private String username="root";
    private String password="joy123";
    private String url="jdbc:mysql://localhost:3306/studentdb?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull";


    // jdbc:mysql://127.0.0.1:3306/studentdb?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull";

    /**
     * 初使化数据库连接
     */
    public void init(){
        try {
            //1.加载驱动
            Class.forName(driverName);
            //2.连接数据库
            conn = DriverManager.getConnection(url,username,password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    /**
     * 支持增删改
     * @param sql
     */
    public void insert(String sql){
        Statement state= null;   //容器
        try {
            state = conn.createStatement();
//            String sql="insert into xs values('1108','张伟','汉企')";   //SQL语句
            state.executeUpdate(sql);         //将sql语句上传至数据库执行


        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            try {
                conn.close();//关闭通道
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 只支持查询
     * @param sql
     * @return
     */
    public List<String> query(String sql){
        Statement state= null;   //容器
        List<String> strings = new ArrayList<>();
        try {
            state = conn.createStatement();
            ResultSet resultSet = state.executeQuery(sql);
            while (resultSet.next()){
                String str = "";
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String password = resultSet.getString("password");
                String number = resultSet.getString("number");
                int sex = resultSet.getInt("sex");
                str = "id:"+id+" name:"+name+" password:"+password+" number:"+number+" sex:"+sex;
                strings.add(str);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return strings;
    }

}