第八章项目这部分听不懂怎么办？

package util;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.Statement;

public class DBHelper{

private static  final String driver  = "com.mysql.jdbc.Driver";//数据库驱动

//连接数据库的URL地址

private static final String url = "jdbc:mysql://localhost:3306/shopping?useUnicode=true"

+ "&characterEncoding=UTF-8";

private static final String username = "root";//数据库的用户名

private static final String password = "123456";//数据库的密码

private static  Connection conn;

//静态代码块负责加载驱动

static 

{

try

{

Class.forName(driver);

}

catch(Exception ex)

{

ex.printStackTrace();

}

}

//单例模式返回数据库连接对象

public static Connection getConnection() throws Exception

{

if(conn==null)

{

conn = DriverManager.getConnection(url, username, password);

}

return conn;

}

public static void main(String[] args) {

try

{

Connection conn = DBHelper.getConnection();

if(conn!=null)

{

System.out.println("数据库连接正常！");

}

else

{

System.out.println("数据库连接异常！");

}

}

catch(Exception ex)

{

ex.printStackTrace();

}

}

}