The Shipper and Shipment classes are part of a delivery system. They handle different types of items (like letters, packages, or oversized items) that need to be delivered to various places.
The job of the Shipper is to figure out the cost to deliver an item based on its type and weight.
The Shipment classes represent the different items to be delivered. Each item has a ship method that determines how it's delivered and a getCost method that figures out the delivery cost.
The ShipmentFactory class makes it easy to create new items based on the item's weight. The items that are created can be decorated with extra features using the ShipmentDecorator, like marking if an item is fragile or if a delivery confirmation is needed.