Person接口

Worker类

Person p = new Worler();

p.eat();

JDBC快速入门

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.Statement;

public class JdbcCaiNiao{

    public static void main(String[] args) throws Exception{

        //1.导入驱动jar包

        //2.注册驱动

        Class.forName("com.mysql.jdbc.Driver");

        //3.获取数据库连对象

        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3","root","password");

        //4.定义sql语句

        String sql = "update account set balance = 500 where id = 1";

        //5.获取执行sql语句的对象 Statement

        Statement stmt = conn.createStatement();

        //6.执行sql

        int count = stmt.executeUpdate(sql);

        //7.处理结果

        System.out.println(count);

        //8.释放结果

        stmt.close();

        conn.close();

    }

}