Java Reference
In-Depth Information
To compile
Storefront.java
, the
Item
class must be stored in a folder that corresponds
to the
org.cadenhead.ecommerce
package name. After you have compiled
Storefront.
class
, move the file to the same folder as
Item.class
.
The
Storefront.class
is used to manage a collection of products in an online store.
Each product is an
Item
object, and they are stored together in a
LinkedList
instance
variable named
catalog
(line 6).
The
addItem()
method in lines 8-13 creates a new
Item
object based on four arguments
sent to the method: the ID, name, price, and quantity in stock of the item. After the item
is created, it is added to the
catalog
linked list by calling its
add()
method with the
Item
object as an argument.
The
getItem()
and
getSize()
methods provide an interface to the information stored in
the private
catalog
variable. The
getSize()
method in lines 19-21 calls the
catalog.size()
method, which returns the number of objects contained in
catalog
.
Because objects in a linked list are numbered like arrays and other data structures, you
can retrieve them using an index number. The
getItem()
method in lines 15-17 calls
catalog.get()
with an index number as an argument, returning the object stored at that
location in the linked list.
The
sort()
method in lines 23-25 is where you benefit from the implementation of the
Comparable
interface in the
Item
class. The class method
Collections.sort()
sorts a
linked list and other data structures based on the natural sort order of the objects they
contain, calling the object's
compareTo()
method to determine this order.
After you compile
Storefront
class, you're ready to develop a program that actually
uses the
org.cadenhead.ecommerce
package. Open the folder on your system where
you've been creating the programs of this topic (such as
\J21work
) and create
GiftShop.java
from Listing 6.4.
CAUTION
Don't save
GiftShop.java
in the same folder on your system where
the classes of the
org.cadenhead.ecommerce
package are stored.
It's not part of the package (as you'll note by the absence of a
package org.cadenhead.ecommerce
statement). The Java compiler
exits with an error message because it wasn't expecting to find
Storefront.class
in the same folder as the
GiftShop
application.
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