Download COMP 131: Object-Oriented Programming with Java

COMP 131: Object-Oriented Programming with Java
Spring 2006
Homework Assignment 8
Due by 11:59pm, Sunday, May 14, 2006
QualityManager
BillingItem
VoiceCall
TextMessage
Your task in this problem is to design and implement Java classes for the billing system of a cell
phone service provider. The type hierarchy for the billing system is given above.
The company bills customers for voice calls and text messages. The costs of voice calls and text
messages are computed differently. The company keeps track of the duration of a voice call (in
seconds) and the number of characters in a text message.
The ultimate goal for this system is to print out a billing statement for the cell phone service provider.
Each line of the statement corresponds to a single voice call or text message, and prints all the relevant
information about the call or message. Here is a sample output of the billing statement program.
Call 0 From 2125551212 to 2123381748 was a text message of 0 characters and had cost 0
Call 1 From 2125551212 to 2123381748 was a voice call of duration 450 seconds and had cost 3.90 YTL
Call 2 From 2125551212 to 2123381748 was a text message of 40 characters and had cost 0
Call 3 From 2125551212 to 2123381748 was a text message of 60 characters and had cost 1 YTL
Call 4 From 2125551212 to 2123381748 was a text message of 80 characters and had cost 2 YTL
Call 5 From 2125551212 to 2123381748 was a text message of 100 characters and had cost 3 YTL
Call 6 From 2125551212 to 2123381748 was a voice call of duration 2700 seconds and had cost 26.40 YTL but
was discounted to 13.20 YTL due to low voice quality.
Call 7 From 2125551212 to 2123381748 was a voice call of duration 3150 seconds and had cost 30.90 YTL but
was discounted to 0 due to unacceptable voice quality.
Call 8 From 2125551212 to 2123381748 was a text message of 160 characters and had cost 6 YTL
Call 9 From 2125551212 to 2123381748 was a text message of 180 characters and had cost 7 YTL
Part of the code that tests the billing system is provided in the file BillingTester.java.
Examine this file first, before writing any code. You are required to complete the code in
BillingTester.java and implement the rest of your classes so that BillingTester.java
compiles and executes without errors. Note, especially, that BillingTester.java uses an array of
BillingItem objects to store 10 billing items and calls the cost() method for each object in the
array.
Text messages are priced as follows:
 The first 40 characters of a message are free
 For every extra 10 characters, the charge is 50 YKR
Voice calls are priced as follows:
 The first minute of a voice call is free
 The charge for every extra 10 seconds is 10 YKR
The quality of the connection during a voice call can be HIGH, LOW or UNACCEPTABLE. These
constants are already defined in the enum VoiceQuality. You are required to make use of this
enum when referring to voice quality. If the quality of a connection is HIGH, it is charged as described
above. If the quality is LOW, the call is charged half price. If the quality is UNACCEPTABLE, the
call is free.
The Java interface QualityManager is also provided for you. This interface lists two methods,
reportQuality(), which returns the quality of the call, and discountedCost(), which returns
the discount for the cost of the call if the quality of the connection is not HIGH, as explained above.
VoiceCall is required to implement QualityManager and BillingTester uses methods of this
interface while printing the billing statement for the company.
Part 1-A: Implement a BillingItem class [10 points]
A partial implementation for this class is not provided.
BillingItem must
I.
II.
III.
IV.
have a no-argument constructor,
have a constructor whose arguments are the phone numbers of the caller and destination,
provide a reasonable toString method
provide get and set methods for its fields. The set methods should make sure that the field values
are legal values. Phone numbers are required to be ten-digit numbers. Fields representing phone
numbers must be set to a default value if no properly formatted value is supplied.
V. have other fields/methods as necessary
Make sure that BillingItem does not have fields and/or methods that are never used.
Part 1-B: Implement a VoiceCall class. [15 points]
A partial implementation for this class is not provided
This class should
I. have a no-argument constructor
II. have a constructor whose arguments are the phone numbers of the caller and destination, the
duration of the phone call, and the quality of the voice connection during the phone call
III. provide a reasonable toString method
IV. provide get and set methods for its fields. The set methods should make sure that the field values
make sense.
V. Must implement the interface QualityManager and have methods that compute regular and
discounted call prices as explained above
VI. have any other fields and methods as necessary
Do not unnecessarily override methods. Do not duplicate work already done in the superclass.
Part 1-C: Implement a TextMessage class [15 points]
A partial implementation for this class is not provided
This class should
I. have a no-argument constructor,
II. have a constructor whose arguments are the phone numbers of the caller and destination, and the
length of the voice message,
III. provide a reasonable toString method,
IV. provide get and set methods for its fields. The set methods should make sure that the field values
make sense.
V. have any other fields/methods as necessary
Do not unnecessarily override methods. Do not duplicate work already done in the superclass
BillingItem.
Part 1-D: Complete the implementation of the BillingTest class [10 points]
Most of the implementation for this class is given. You are only required to add code in a designated
place in this class in order to print the discounted price of a call when appropriate.