week04
ICT167 Principles of Computer Science
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Lab Practice Week 4
You need to show working versions of your answers to all questions to your tutor.
Your tutor will expect to see them by your next session.
What to submit: your answers to exercises 1, 2, 6, 7, and 8.
Note: even though you only need to submit those exercises mentioned above, you
should attempt all exercises in each lab practice to help
oaden your
understanding; this may also help with your assignment work.
Do all the programs in NetBeans IDE.
NOTE: Include internal documentation in your code, if you are not sure, read
chapter 2.4 in your textbook and talk to your lecturer
This week exercise builds on the Fraction class which you produced for exercises 1,
3, 4, and 5 in last week’s lab practice.
Before starting the exercises, make sure you have read the relevant material.
1. Add another public method called add() to your Fraction class. This method
adds another fraction to the ‘calling object’. Thus, the method will take a
Fraction class object as a parameter, add this parameter fraction to the calling
object (fraction), and return a Fraction object as a result. HINT: we can use
cross multiplication to determine the numerator of the resultant Fraction. The
denominator of the resultant Fraction is simply the multiplication of the
denominators of the two other Fractions.
2. Write a client program that loops around getting two fractions from the user,
output their sum, and state whether or not they are equal. Keep looping until
the first fraction entered is a zero fraction.
3. Update your UML diagram from last week to include the added behaviour of
your Fraction class.
4. Add another public method dblValue() to your Fraction class which returns the
double precision approximation value of the fraction. That is, the floating
point result of actually dividing numerator by denominator. N.B. this method
does not do any display itself, but can be called by a client program to be used
in an output statement. Eg: if a client has a fraction frac that represents 1 / 2,
then a method call to frac.dblValue() should return the double number 0.5.
Use your client program to test this functionality; i.e. provide an output
statement to display the double value of a fraction.
ICT167 Principles of Computer Science
2
5. Add a toString() method to your Fraction class that returns the fraction as a
String in the form "x / y", where x and y are numerator and denominator
espectively. This is similar to your display method, but it does not actually do
any output itself; it only returns the Fraction as a String -- nothing else. N.B.
as the method does not do any display itself, the output can be done by a
client program that calls the method in an output statement. Use your client
program to test this functionality; i.e. provide an output statement to display a
fraction as its String representation.
6. Add a private method simplify() to your Fraction class that converts a fraction
to its simplest form. For example, the fraction 20 / 60 should be stored in the
class instance variables as 1 / 3 (i.e. numerator = 1, denominator = 3). N.B.
you will need a method to determine the Greatest Common Divisor (GCD.
Remember, both of these methods (simplify and gcd) must be private. As
these methods are private, client programs cannot access them. So, how are
they to be used? They can only be accessed within the Fraction class. Given
their purpose, it would mean that any Fraction class method that modifies the
instance variables (e.g.: input, add, constructor, set) should call the simplify()
method to reduce the instance variables to their minimum values. Thus, these
methods are used only for housekeeping; they are not to be used by client
programs.
7. Write a client program that allows the user to add up any number of non-zero
fractions. The program should display the running total as an exact fraction (in
simplified form as numerator / denominator), and as an approximate double
value. The user can finish by entering a fraction that represents a zero fraction.
8. Update your UML diagram from point 3 to include all added behaviour of
your Fraction class.