Why would you declare an Interface and then instantiate an object with it in Java?

Question

A friend and I are studying Java. We were looking at interfaces today and we got into a bit of an discussion about how interfaces are used.

The example code my frie

Answer 1

With "IVehicle modeOfTransport1 = new Car();", methods owned only by Car are not accessible to modeOfTransport1. I don't know the reason anyway.