Picture of the Classes

Here is a picture that shows the classes and the interface. The children classes extend their parent. This is shown with a solid arrow pointing at the parent.

The solid arrows show inheritance. The three children inherit the display() method from their parent, Goods.

Two of the classes implement the interface. This is shown with a dotted arrow pointing at the interface.

The dotted arrows show what a class must implement. The Toy and Book classes must implement the calculateTax() method.