Java连接MySQL数据库

package sqldemo;
import java.sql.*;
public class demo1 {
    public static void main(String[] args) throws Exception {
        Connection con;//声明Connection对象
        String driver="com.mysql.jdbc.Driver";//驱动程序名
        //URL指向要访问的数据库名(db_demo)，出现Unknown initial character set index ‘255‘ received from server错误时
        //在URL后面加"?useUnicode=true&characterEncoding=utf8"设置编码方式，
        String url="jdbc:mysql://localhost:3306/db_demo?useUnicode=true&characterEncoding=utf8";
        String user="root";//MySQL配置时的用户名
        String password="123456";//MySQL配置时的密码
        Class.forName(driver);//加载驱动程序
        con=DriverManager.getConnection(url, user, password);//getConnection()方法连接数据库
        System.out.println(con);
        if (!con.isClosed()) {
            System.out.println("Succeeded connecting to the Database!");                
        }
        Statement statement=con.createStatement();//创建Statement类对象，用于执行SQL语句
        String sql="select* from categories";//要执行的SQL语句
        ResultSet rs=statement.executeQuery(sql);//ResultSet类，用于存放获取的结果集
        System.out.println("编号" + "\t" + "书名");  
        int id=0;
        String name=null;
        while(rs.next()){
            id=rs.getInt("id");//获取数据表categories中id这列数据
            name=rs.getString("typeName");//获取数据表categories中typeName这列数据
            System.out.println(id+"\t"+name);        
        }
        rs.close();
        con.close();
    }
}