import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public final class JDBCUtils {
    private static String url = "jdbc:mysql://localhost:3306/jdbc";
    private static String user = "root";
    private static String password = "six";
    private JDBCUtils(){
    }
    static{
        // 1.注册驱动
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            throw new ExceptionInInitializerError(e);
        }
    }
    public static Connection getConnection() throws SQLException{
        return DriverManager.getConnection(url, user, password);
    }
    public static void free(ResultSet rs,Statement st,Connection conn){
        try{
            if(rs!=null){
                rs.close();
            }
        }catch(SQLException e){
            e.printStackTrace();
        }finally{
            try{
                if(st != null){
                    st.close();
                }
            }catch(SQLException e){
                e.printStackTrace();
            }finally{
                if(conn!=null){
                    try {
                        conn.close();
                    } catch (SQLException e) {
                       e.printStackTrace();
                    }
                }
            }
        }
    }
}

main.java

import java.sql.Connection;

import java.sql.ResultSet;

import java.sql.Statement;



public class main {



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

        // TODO Auto-generated method stub

        template();

    }



    static void template() throws Exception{



        Connection conn = null;

        Statement st = null;

        ResultSet rs = null;



        try {



            // 2.建立连接             conn = JDBCUtils.getConnection();



            // 3.创建语句             st = conn.createStatement();



            // 4.执行语句             rs = st.executeQuery("select * from user");



            // 5.处理结果             while(rs.next()){

                System.out.println(rs.getObject(1) + "\t" + rs.getObject(2)

                        + "\t"+ rs.getObject(3)+"\t" + rs.getObject(4));

            }

            rs = st.executeQuery("select * from user2"); //再次查询             while(rs.next()){

                System.out.println(rs.getObject(1) + "\t" + rs.getObject(2)

                        + "\t"+ rs.getObject(3)+"\t" + rs.getObject(4));

            }

        }finally{

            JDBCUtils.free(rs, st, conn);

        }

    }

}