编写配置文件【db.properties】：

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcStudy?useUnicode=true&characterEncoding=utf8&useSSL=true
username=root
password=admin#1234

编写连接数据库的工具类【JdbcUtils】

package com.yeyue.lesson02;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JdbcUtils {

    private static String dirver = null;
    private static String url = null;
    private static String username = null;
    private static String password = null;

    static {
        try{
            //读取到配置文件
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);
            //获取到配置文件中的有用参数
            dirver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
            //加载驱动
            Class.forName(dirver);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        //连接数据库
        return DriverManager.getConnection(url,username,password);
    }

    public static void release(Connection conn, Statement st, ResultSet rs){
        //关闭连接
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(st!=null){
            try {
                st.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}

删除【delete】

package com.yeyue.lesson03;

import com.yeyue.lesson02.JdbcUtils;

import java.sql.*;

public class TestDelete {
    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = JdbcUtils.getConnection();

            String sql = "DELETE FROM users  WHERE id = ?";

            st = conn.prepareStatement(sql);

            st.setInt(1,6);

            int i = st.executeUpdate();
            if(i>0){
                System.out.println("删除成功");
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

新增【insert】

package com.yeyue.lesson03;

import com.yeyue.lesson02.JdbcUtils;
import java.util.Date;
import java.sql.*;

public class TestInsert {
    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = JdbcUtils.getConnection();
            //INSERT INTO `users` (id,NAME,PASSWORD,email) VALUES (6,'wewwqw','2323','323wwqd')
            String sql = "INSERT INTO `users` (id,NAME,PASSWORD,email,birthday) VALUES (?,?,?,?,?)";

            st = conn.prepareStatement(sql);  //预编译sql 不执行

            st.setInt(1,7);
            st.setString(2,"wewwqw");
            st.setString(3,"2323");
            st.setString(4,"323wwqd");
            //java.sql.Date 数据库  java.util.Date java  new Date().getTime() 获取时间戳
            st.setDate(5,new java.sql.Date(new Date().getTime()));

            int i = st.executeUpdate();
            if(i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

改【update】

package com.yeyue.lesson03;

import com.yeyue.lesson02.JdbcUtils;

import java.sql.*;

public class TestUpdate {
    public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try {
            conn = JdbcUtils.getConnection();

            String sql = "UPDATE users SET NAME = 'yeyue1111' WHERE id = ?";

            st = conn.prepareStatement(sql);

            st.setInt(1,4);

            int i = st.executeUpdate();
            if(i>0){
                System.out.println("更新成功");
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}