suitable driver not found

The code given below gives an exception as:
a suitable driver not found.

I am not working on a network, it is a simple stand alone PC.

Which jdbc driver would be suitable,I am using postgreSQL 7.3,j2sdk1.4.2 and have installed jdbc driver pg73jdbc3.jar

import java.sql.*;
class mycon{
public static void main (String args[]) {


try{
Class.forName("org.postgresql.Driver");
String url="jdbc:postgresql://127.0.0.1:5432/a;
Connection con = DriverManager.getConnection(url, "postgres", "");

}catch(ClassNotFoundException e) {
System.out.println("Exception");
System.out.println(e.toString());
}
catch(SQLException e) {
System.out.println("Exception");
System.out.println(e.toString());
}
}
}

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