Java通过接口或者抽象类调用方法的时候，怎么知道调用的是哪个实现类里的方法？

Connection conn = JDBCUtils.getConnection();
System.out.println(conn.getClass());

 1 package cn.itcast.utils;
 2 
 3 import com.alibaba.druid.pool.DruidDataSourceFactory;
 4 
 5 import javax.sql.DataSource;
 6 import java.io.IOException;
 7 import java.sql.Connection;
 8 import java.sql.ResultSet;
 9 import java.sql.SQLException;
10 import java.sql.Statement;
11 import java.util.Properties;
12 
13 public class JDBCUtils {
14     private static DataSource ds;
15 
16     static{
17         Properties pro = new Properties();
18         try {
19             // 1.加载配置文件
20             pro.load(JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"));
21             // 2.获取DataSource
22             ds = DruidDataSourceFactory.createDataSource(pro);
23         } catch (IOException e) {
24             e.printStackTrace();
25         } catch (Exception e) {
26             e.printStackTrace();
27         }
28     }
29 
30 
31     public static DataSource getDataSource(){
32         return ds;
33     }
34     /**
35      * 获取连接
36      * @return
37      * @throws SQLException
38      */
39     public static Connection getConnection() throws SQLException {
40         return ds.getConnection();
41     }
42 
43 
44     public static void close(Statement stmt, Connection conn){
45         if(stmt != null){
46             try {
47                 stmt.close();
48             } catch (SQLException e) {
49                 e.printStackTrace();
50             }
51         }
52 
53         if(conn != null){
54             try {
55                 conn.close();
56             } catch (SQLException e) {
57                 e.printStackTrace();
58             }
59         }
60     }
61 
62 
63     public static void close(ResultSet rs, Statement stmt, Connection conn) {
64         if (rs != null) {
65             try {
66                 rs.close();
67             } catch (SQLException e) {
68                 e.printStackTrace();
69             }
70         }
71         if (stmt != null) {
72             try {
73                 stmt.close();
74             } catch (SQLException e) {
75                 e.printStackTrace();
76             }
77         }
78 
79         if (conn != null) {
80             try {
81                 conn.close();
82             } catch (SQLException e) {
83                 e.printStackTrace();
84             }
85         }
86     }
87 
88 
89 }