Hi I need help with the following question: 2. Chapter 8: Programming Project #1

Question

Hi I need help with the following question:

2. Chapter 8: Programming Project #1 “Rational Number”
a. Download the attached “RationalNumber.java” (The file is at the bottom)

b. Background: a rational number represents a fraction, e.g. 3 / 5. Here, 3 is the numerator,
and 5 is the denominator; both are integers (can be either positive or negative). The
denominator cannot be 0.

c. Implement two constructors:

public RationalNumber(int numerator, int denominator)
It constructs a new rational number. You can assume that the denominator will never be 0.

public RationalNumber()
It constructs a new rational number to represent 0 / 1

d. Implement the two accessors:

public int getDenominator()
It returns this rational number’s denominator. For example, for 3 / 5, it returns 5.

public int getNumerator()
It returns this rational number’s numerator. For example, for 3 / 5, it returns 3.

e. Implement the toString method:
public String toString()
-- It returns a String representation of this rational number, such as “3/5”.
-- If the denominator is 1, omit it. For example, for 4 / 1, it returns “4”.
-- If the numerator is 0, omit denominator. For example, for 0 / 8, it returns “0”.
-- If both of the numerator and the denominator are negative, return positive. For
example, for -3 / -5, it returns “3/5”. CS 210 W. Li Assignment 8
-- If the numerator is positive and the denominator is negative, return the negative
sign in front of the numerator. For example, for 3 / -5, it returns “-3/5”
-- You do NOT need to worry about reduced form (e.g. for 3 / 6, just returns “3/6” is
good enough, no need to return “1/2”).

f. Implement the methods to add, subtract, multiply and divide another rational number.
Here is the “method signature” for add:
public RationalNumber add(RationalNumber numberToAdd)

In the method, you should compute and return the result for the addition. For example,
if r1 is 3 / 5, r2 is -1 / 5, r1.add(r2) should return a value of 2 / 5.

Whether you choose to update the value of r1 is your choice -- in other words, it won’t
affect your grade, as long as the value returned from the method is correct.

Again, you don’t need to worry about reduced form.

Explanation / Answer

public class RationalNumber {

   // TODO: implement the following methods
   int numerator;
   int denominator;

   public RationalNumber(int numerator, int denominator) {
       if (denominator == 0)
           denominator = 1;

       // Make the numerator "store" the sign
       if (denominator < 0) {
           numerator = numerator * -1;
           denominator = denominator * -1;
       }

       this.numerator = numerator;
       this.denominator = denominator;
   }

   public RationalNumber() {
       numerator = 0;
       denominator = 1;
   }

   public int getDenominator() {
       return denominator;
   }

   public int getNumerator() {
       return numerator;
   }

   public String toString() {

       String result;

       if (numerator == 0)
           result = "0";
       else if (denominator == 1)
           result = numerator + "";
       else
           result = numerator + "/" + denominator;

       return result;
   }

   public RationalNumber add(RationalNumber other) {
       int commonDenominator = denominator * other.getDenominator();
       int numerator1 = numerator * other.getDenominator();
       int numerator2 = other.getNumerator() * denominator;
       int sum = numerator1 + numerator2;

       return new RationalNumber(sum, commonDenominator);
   }

   public RationalNumber subtract(RationalNumber other) {
       int commonDenominator = denominator * other.getDenominator();
       int numerator1 = numerator * other.getDenominator();
       int numerator2 = other.getNumerator() * denominator;
       int difference = numerator1 - numerator2;

       return new RationalNumber(difference, commonDenominator);
   }

   public RationalNumber multiply(RationalNumber other) {
       int numer = numerator * other.getNumerator();
       int denom = denominator * other.getDenominator();

       return new RationalNumber(numer, denom);
   }

   public RationalNumber divide(RationalNumber other) {
       return multiply(other.reciprocal());
   }

   public RationalNumber reciprocal() {
       return new RationalNumber(denominator, numerator);
   }

   private void reduce() {
       if (numerator != 0) {
           int common = gcd(Math.abs(numerator), denominator);

           numerator = numerator / common;
           denominator = denominator / common;
       }
   }

   private int gcd(int num1, int num2) {
       while (num1 != num2)
           if (num1 > num2)
               num1 = num1 - num2;
           else
               num2 = num2 - num1;

       return num1;
   }

   public static void main(String[] args) {
       RationalNumber rationalNumber1 = new RationalNumber(5, 2);
       RationalNumber rationalNumber2 = new RationalNumber(2, 3);
       System.out.println("Addition of r1 and r2:"
               + rationalNumber1.add(rationalNumber2));
       System.out.println("Subtraction of r1 and r2:"
               + rationalNumber1.subtract(rationalNumber2));
   }
}

OUTPUT:

Addition of r1 and r2:19/6
Subtraction of r1 and r2:11/6

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