CS 110 Spring 2009
Program 4
Learning Objectives
Demonstrate the ability to write a simple Java project
that includes a user-defined class: Fraction
Demonstrate how to use instance variables and
methods in your user-defined class
Demonstrate the use of objects in your driver program
Understand simple decision making concepts.
Program 4 Assignment
This assignment builds on the two .java files you did for Lab4.
Begin by copying from your Lab4 folder, the Fraction.java and
FractionDemo.java files, to your Program4 folder.
Expand your Fraction class from Lab 4 by adding five more
instance methods: add, subtract, multiply, divide, and a
method to determine if the fraction is a proper or improper
fraction. In a proper fraction, the numerator is less than the
denominator; in an improper fraction the numerator is greater
than or equal to the denominator. Please take note of the
isProperFraction( ) method’s return type designated in the UML
diagram.
Methods add, subtract, multiply, and divide should accept a
Fraction argument passed as the parameter and return a
Fraction.
The toString( ) method of the Fraction class should declare a
local boolean variable, which is set to either true or false by calling the isProperFraction( )
method. Inside the toString( ) there will be an if / else decision making process which depends
on the value returned from the isProperFraction( ) method. A different String message is
returned, depending on which of these if / else statements execute.
In your FractionDemo main method, implement the following:
1. Read in the numerator and demoninator for two Fraction objects from the user.
2. Display their values as fractions (using toString). Recall that the toString( ) method
will display whether the fraction is proper or improper.
3. Display the results of the four arithmetic methods.
Fraction Arithmetic
In case you have forgotten your fraction arithmetic, here is a quick crib sheet for addition,
subtraction, multiplication, and division. Do not worry about reducing your fractions
(e.g. 4 / 8 is fine, do not reduce it to 1 / 2)
Page 1 of 3
Fraction
- numerator : int
- denominator : int
+ Fraction (n: int, d: int)
+ setNumerator (n: int) : void
+ getNumerator ( ) : int
+ setDenominator (d: int) : void
+ getDenominator ( ) : int
+ setFraction (n: int, d:int) : void
+ getAsDouble ( ) : double
+ isProperFraction( ) : boolean
+ toString ( ) : String
+ add (f2: Fraction): Fraction
+ subtract (f2: Fraction): Fraction
+ multiply (f2: Fraction): Fraction
+ divide (f2: Fraction): Fraction
