CSE110 - Assignment #6  - Solved

Topics 

•         Object Oriented Programming & Methods (Chapter 5 & 8)  

-   Tester class development (Command Menu)  

-   Implementing instance methods  

Use the following Guidelines: 

•         Give identifiers semantic meaning and make them easy to read (examples numStudents, grossPay, etc).  

•         Keep identifiers to a reasonably short length.  

•         User upper case for constants. Use title case (first letter is upper case) for classes. Use lower case with uppercase word separators for all other identifiers (variables, methods, objects).  

•         Use tabs or spaces to indent code within blocks (code surrounded by braces). This includes classes, methods, and code associated with ifs, switches and loops. Be consistent with the number of spaces or tabs that you use to indent.  

•         Use white space to make your program more readable.  

 

Part 1: There are no written exercises in this assignment Part 2: Programming (20 points): 

1)                  Write a class definition (not a program, there is no main method) named Fraction (saved in a file Fraction.java) that calculates the math operations as a fraction. A Fraction is an object with two integers, numerator and denominator. A new Fraction object starts as 0 (0/1). The test program asks to choose the operation (+, -, *, or /) and type two integers as one single line. Then, the Fraction shows the operation and result.  

 

Your Fraction class must have: •        two instance variables 

𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟

 – the numerator and denominator (Fraction =  ) 

𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟

        •     Must implement the following methods 

 

Methods 
Description of the methods
public Fraction (int numerator, int denominator) 
Constructor-Sets the instance variables with the inputs (2 Pts) 
public String toString() 
It returns the fraction as a string such as "5/3" when the numerator is 5 and denominator 3. 

When the numerator is 0, it returns "0", and when the denominator is "1", it returns the numerator. 3/1 ==> "3"  

(2 Pts) 
 
 It reads two integers and returns the greatest common divisor by using the following algorithm.  

1.                  Create a loop, and subtract the smaller integer from the larger one (if the integers are equal you may choose either one as the “larger”) during each iteration.  

2.                  Replace the larger integer with the computed difference.  

3.                  Continue looping until one of the integers becomes zero.  

For instance, assume that two integers 24 and 18 are given. In the first iteration, the larger item is 24, and the difference is 24 – 18 = 6. In the next iteration, 24 is replaced with 6 so the larger item is set as 18, and the difference is 18 – 6= 12. In the third iteration, 18 is replaced with 12 so the larger item is set as 12, and the difference is 12 – 6 = 6. Now two items are both 6, so the difference is 0, then stop the loop and return 6. 

(Not allowed to use Recursive approach: -3 Pts) 
private
 int greatestCommonDivisor (int num1, m2) 
int nu
 
It simplifies the fraction.  

Case-1: When the denominator is negative, multiply -1 with both denominator and numerator. For example, 2/-3 
private
 void simplify() 
 
 
==> -2/3 

Case-2: When the numerator and denominator are not coprime (relatively prime), divide both by their greatest 
common divisor
. For example, 4/12 ==> 1/3    (2 Pts) 
public Fracti
static
 Fraction multiply (Fraction a, 
It takes two Fractions, and returns the result of multiplication of them, a * b. (1 Pts) 
on b) 
public 

Fraction b
static
 Fraction divide (Fraction a, 
It takes two Fractions, and returns the result of division of them, a / b. (1 Pts) 
) 
public static Fraction add (Fraction a, Fraction b) 
It takes two Fractions, and returns the result of addition of them, a + b. (2 Pts) 
public static Fraction subtract (Fraction a, Fraction b) 
It takes two Fractions, and returns the result of subtraction a - b. (2 Pts) 
 

 

2)                  Download and complete (fill out the missing code) the test driver called Assignment6.java  (5 Pts). Assignment6.java contains the main method and creates a new Fraction object to test the methods in the class Fraction.  Assignment6.java will ask a user to enter one of the following commands. Based on the user's choice, the program needs to perform corresponding operation. This will be done by calling (invoking) one of the methods you defined in the Fraction class. The program will terminate when the user enters 'q'. 

 

Command Options 

----------------------------------- c: reset the value 

+: add a fraction to the current value 

-: subtract a fraction from the current value  

*: multiply a fraction to the current value 

/: divide the current value by a fraction 

?: display the menu again 

q: quit this program 

 

Here is the description for each option: 

command 
task 
c 
resets the global Fraction as 0. (0/1) 
+ 
asks to type two integers and construct a new Fraction. Calculate and display the value of global Fraction and the  new Fraction. The result is set as the current Fraction so that the additional operation can be made. 
- 
asks to type two integers and construct a new Fraction. Calculate and display the value of global Fraction and the  new Fraction. The result is set as the current Fraction so that the additional operation can be made. 
* 
asks to type two integers and construct a new Fraction. Calculate and display the value of global Fraction and the  new Fraction. The result is set as the current Fraction so that the additional operation can be made. 
/ 
asks to type two integers and construct a new Fraction. Calculate and display the value of global Fraction and the  new Fraction. The result is set as the current Fraction so that the additional operation can be made. 
? 
displays the menu 
q 
quits the program 
 

You must complete the code inside cases 'c', '+', '-', '*' and '/'' to read the needed input, call the appropriate method of the Fraction class, and display an appropriate output. A sample output is shown below. 

 

Helpful hints for doing this assignment:  

•      work on it in steps – write one method, test it with a test driver and make sure it works before going on to the next method  

•      always make sure your code compiles before you add another method  

•      your methods should be able to be called in any order  

•      Operation of Factions: The result is also a Fraction, which needs two values of new numerator and denominator as shown below.  

 

                        < 𝐴 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 >        < 𝐵 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 >

A ∗ B =   ∗      

                     < 𝐴 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >    < 𝐵 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >

 

                           < 𝐴 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 > ∗ < 𝐵 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 >            𝑛𝑒𝑤 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟

             =  =     

                      < 𝐴 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 > ∗ < 𝐵 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >      𝑛𝑒𝑤 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟

 

                         < 𝐴 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 >         < 𝐵 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 >

A + B =   +   

                       < 𝐴 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >      < 𝐵 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >

            

< 𝐴 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜𝑟 > ∗ < 𝐵 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 > + < 𝐵 𝑛𝑢𝑚𝑒𝑟𝑎𝑡𝑜 > ∗< 𝐴 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >

=   

< 𝐴 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 > ∗ < 𝐵 𝑑𝑒𝑛𝑜𝑚𝑖𝑛𝑎𝑡𝑜𝑟 >

 

 

Sample Output (user input is in red, which will not seen online submission): 

---------------- 

INPUT 1 

---------------- 

c 

+ 

3 5 

+ 

1  2 

- 

2  3 

* 4 7 c 

+ 

4 2 

/ 

12 8 

? q 

 

---------------- YOUR OUTPUT 1 

---------------- 

*** Start of Program *** 

 

Command Options 

----------------------------------- c: reset the value 

+: add a fraction to the current value 

-: subtract a fraction from the current value 

*: multiply a fraction to the current value 

/: divide the current value by a fraction 

?: display the menu again q: quit this program 

 

Value:0 

 

[Please enter a command or type ?] c 

Value:0 

 

[Please enter a command or type ?] + 

[Enter two numbers for a fraction to ADD] 3 5 

0 + 3/5 = 3/5 

Value:3/5 

 

[Please enter a command or type ?] + 

[Enter two numbers for a fraction to ADD] 1 2 

3/5 + 1/2 = 11/10 

Value:11/10 

 

[Please enter a command or type ?] - 

[Enter two numbers for a fraction to SUBTRACT] 2 3 

11/10 - 2/3 = 13/30 

Value:13/30 

 

[Please enter a command or type ?] * 

[Enter two numbers for a fraction to MULTIPLY] 4 7 

13/30 * 4/7 = 26/105 

Value:26/105 

 

[Please enter a command or type ?] c 

Value:0 

 

[Please enter a command or type ?] + 

[Enter two numbers for a fraction to ADD] 4 2 

0 + 4/2 = 2 

Value:2 

 

[Please enter a command or type ?] / 

[Enter two numbers for a fraction to DIVIDE]  12 8 2 / 12/8 = 4/3 

Value:4/3 

 

[Please enter a command or type ?] ? 

 

Command Options 

----------------------------------- c: reset the value 

+: add a fraction to the current value 

-: subtract a fraction from the current value 

*: multiply a fraction to the current value 

/: divide the current value by a fraction 

?: display the menu again q: quit this program 

 

Value:4/3 

 

[Please enter a command or type ?] q 

*** End of Program ***