讲解MSc/ICY、辅导Java设计、辅导Software、讲解Java程序设计
- 首页 >> Java编程c Manfred Kerber School of Computer Science
Alexandros Evangelidis University of Birmingham
Worksheet 8 Wednesday 21 November 2018
MSc/ICY Software Workshop
Assessed Worksheet: 2% of the module mark.
Submission Deadline is Thursday, 6 December 2018, at 2pm via Canvas.
5% late submission penalty within the first 24 hours. No submission after 24 hours. Follow
the submissions guidelines on Canvas. JavaDoc comments are mandatory. This worksheet will
be vivaed. No public tests will be provided, but you should still write your own JUnit tests.
Exercise 1: (Basic, 30%) In the lecture (see the Canvas pages for Week 7) we have seen in a package
company an abstract class Employee with two subclasses HourlyEmployee and MonthlyEmployee. Adapt
these classes (and the interface Payable) so that the salary is of type double. Write a class Company with
field variable ArrayList<Employee> employees with the usual getter and setter. Furthermore write in
the Company class a method public void increaseSalaries(double rate) which increases the salaries
of all employees (whether paid on an hourly rate or with a fixed monthly salary) by the fixed rate. (Note,
it makes sense to have corresponding increaseSalary methods – abstract or not – in the three classes
dealing with employees.)
For instance, with a pay increase of 0.02, somebody earning ￡10 per hour would then earn ￡10.20 per
hour and somebody earning ￡1800 a month would then earn ￡1836 per month. That is, the method
increaseSalaries should go over the whole ArrayList of all employees and increase all their salaries.
Exercise 2: (Medium, 30%)
(a) Implement a shopping cart. The customer can add products to the shopping cart and can inspect
the current state by printing it. The two classes, Product and ShoppingCart should reside in the
package shop.
The class Product should have the three field variables private String name, private double
price, and private int quantity with a standard constructor and standard getters. The field
price stores the price for a single product. The class should also contain a method public double
getTotalPrice(), which computes the total price by multiplying the single price and the quantity.
The class ShoppingCart has to contain a constructor public ShoppingCart(), a toString method
and a method public void add(Product p) to add a product to the shopping cart. Note that
products with the same name and price should not be added multiple times to the ArrayList, but
that their quantity is to be adjusted.
For instance, a shopping cart containing the three products Product("Milk (1l)", 1.12, 2),
Product("Bread", 0.78, 2), and Product("Apples", 0.49, 4) should be printed as:
2 * GBP 1.12 Milk (1l) = GBP 2.24
2 * GBP 0.78 Bread = GBP 1.56
4 * GBP 0.49 Apples = GBP 1.96
---------------
TOTAL GBP 5.76
Note that prices should be rounded and displayed to exactly two digits after the decimal point.
(b) Introduce multibuy discounts using a class public class MultiBuyProduct extends Product
with constructor public MultiBuyProduct(String name, double price, int quantity, int
minDiscountedQuantity, int discountPercent) and method public double getTotalPrice().
new MultiBuyProduct("Tomato", 0.5, 20, 10, 3) means that you buy 20 tomatoes at a price
of ￡0.50 and since you buy at least 10 you get a discount of 3%. MultiBuyProduct should reuse
functionality from its superclass wherever possible.
For instance, a shopping cart created by adding the products Product("Milk (1pt)", 0.79, 9),
MultiBuyProduct("Tomato", 0.5, 20, 10, 3), Product("Tomato", 0.53, 5), and Product("Milk
(1pt)", 0.79, 4) should be printed as:
13 * GBP 0.79 Milk (1pt) = GBP 10.27
20 * GBP 0.50 Tomato = GBP 9.70
(Multibuy Discount: GBP 0.30)
5 * GBP 0.53 Tomato = GBP 2.65
---------------
TOTAL GBP 22.62
Exercise 3: (Advanced, 30%) For this exercise you may make use of the Date class from the lab
lecture of Week 4. Write a program that allows users to book a number of rooms. Concretely, it should
be possible to book a room by a method public boolean book(String room, Date date, int hour,
String purpose) where the room is taken from a fixed number of rooms such as String[] rooms =
{"R217", "R222", "R225", "R245"}, date is a date such as Date nov22 = new Date(22, "November",
2018), hour is the hour of the day for which the room is needed such as 14 to book the room from 14:00
to 15:00, and purpose describes what the room is needed for. It should be possible to construct objects
by:
RoomBooking bookings2018 = new RoomBooking(2018, rooms).
The method book returns true if the room is available, false else. Bookings can be made for hours
starting at 9:00, 10:00, . . ., 17:00.
Write also a method public void cancel(String room, Date date, int hour) that deletes a booking
if it exists, so that the room is again available for further bookings. It should do nothing if the booking
does not exist.
For instance, it should be possible to make bookings such as:
bookings2018.book("R222", nov22, 12, "Tutor meeting");
bookings2018.book("R222", nov22, 12, "Java meeting"); //no booking since room booked already
bookings2018.book("R222", nov22, 13, "Interviews");
bookings2018.book("R245", nov22, 16, "Project meeting");
bookings2018.book("R225", nov22, 14, "Top-up tutorial");
Write also a method public String displayDay(Date date) so that bookings2018.displayDay(nov22)
produces a String such as:
22 November 2018
| R217 | R222 | R225 | R245 |
------+--------------------+--------------------+--------------------+--------------------+
9:00| | | | |
------+--------------------+--------------------+--------------------+--------------------+
10:00| | | | |
------+--------------------+--------------------+--------------------+--------------------+
11:00| | | | |
------+--------------------+--------------------+--------------------+--------------------+
12:00| | Tutor meeting | | |
------+--------------------+--------------------+--------------------+--------------------+
13:00| | Interviews | | |
------+--------------------+--------------------+--------------------+--------------------+
14:00| | | Top-up tutorial | |
------+--------------------+--------------------+--------------------+--------------------+
15:00| | | | |
------+--------------------+--------------------+--------------------+--------------------+
16:00| | | | Project meeting |
------+--------------------+--------------------+--------------------+--------------------+
17:00| | | | |
------+--------------------+--------------------+--------------------+--------------------+
Exercise 4: (Debugging, 10%) In the folder Ex4 on Canvas you find a class PGMImage that contains
a method public void rotate (String filename) that should rotate a PGMImage by 90?
clockwise and
write it to a file filename. However, tests with images show that the images are not correctly rotated.
What is the problem? Fix it.