Who implements Connection, ResultSet and Statement interfaces in this java program? [duplicate]

Question

I recently found out that the Statement, Connection and the ResultSet used in the following program are interfaces. This program works completely fine but who implements these interfaces ?

package jdbc;

import java.sql.*;

public class Mango {

    public static void main(String[] args) throws Exception {
        Class.forName("oracle.jdbc.driver.OracleDriver");   
        Connection con = DriverManager.getConnection("jdbc:oracle:thin:@66.66.66.128:1521:xe","SYSTEM","matrix");
        Statement comm = con.createStatement();
        comm.executeQuery("insert into a values('a',1)");
        ResultSet res = comm.executeQuery("SELECT * FROM A");
        comm.executeQuery("insert into a values('a',1)");
        while(res.next()) {
            System.out.println(res.getString(1) + " " + res.getInt(2));
        }
    }

}

Answer 1

Interfaces Statement, Connection and the ResultSet are finally implemented by the third party JDBC Driver provider.

Suppose if you are using MySQL Driver, this is how the hierarchy of implementation follows,

1. java.sql.Statement interface is finally implemented by com.mysql.jdbc.StatementImpl Class.

Internal implementation hierarchy:

com.mysql.jdbc.StatementImpl(Class) -->implements--> com.mysql.jdbc.Statement(interface) -->extends--> java.sql.Statement(interface)

2. java.sql.Connection interface is finally implemented by com.mysql.jdbc.JDBC4Connection Class.

Internal implementation hierarchy:

com.mysql.jdbc.JDBC4Connection(Class) -->extends--> com.mysql.jdbc.ConnectionImp(Class) -->extends--> com.mysql.jdbc.ConnectionPropertiesImpl(Class) -->implements--> com.mysql.jdbc.MySQLConnection(Interface) -->extends--> com.mysql.jdbc.Connection(Interface) -->extends--> java.sql.Connection(Interface)

3. java.sql.ResultSet interface is finally implemented by com.mysql.jdbc.ResultSetImpl Class.

Internal implementation hierarchy:

com.mysql.jdbc.ResultSetImpl(Class) -->implements--> com.mysql.jdbc.ResultSetInternalMethods(Interface) -->extends--> java.sql.ResultSet(Interface)

Answer 2

The JDBC API is implemented through the JDBC driver which are being provided by the various Database software vendors.

The JDBC Driver is a set of classes that implement the JDBC interfaces to process JDBC calls and return result sets to a Java application