Question

Heres an example of what I mean:

public class Rectangle
{
    private int length;
    private int breadth;
    .
    .
}

public class Box extends Rectangle
{
    private int height;
    .
    .
}

When you:

Box b = new Box();

Does it create a Box as well as a Rectangle object, with the rectangle not directly accessible, but only accessible through the Box object. In other words, does it create two objects in memory?

Answer 1

In other words, does it create two objects in memory?

No, it creates a single object. This single object represents a Box (and since this is a subtype of Rectangle this same object represents a Rectangle as well).

The inheritance simply ensures that the interface of the Box object is an extension of the Rectangle interface.