Looping program using a boolean method in Java

Question

I have two classes.

import java.util.Scanner;
public class Fraction
{
  private int numerator;
  private int denominator;

  public void inputValues()
  {
    Scanner kb = new Scanner(System.in);
    System.out.println("Enter your numerator: ");
    numerator = kb.nextInt();
    System.out.println("Enter your denominator: ");
    denominator = kb.nextInt();                   
  }

  public int getNumerator()            //GetMethod
  {return numerator;}


  public boolean isZero()
  {
    if (getNumerator ==0)
    return false;
  }
}

I want my program to stop looping once the value for numerator is 0. and I've made a silly mistake somewhere but I cant seem to see it or figure out why. Many thanks in advance and much appreciated.

public class FractionDemo{
  public static void main (String[]argv) {
    Fraction f1 = new Fraction();
    Fraction f2 = new Fraction();
    f1.inputValues();
    f2.inputValues();

    while(f1.isZero())
    {
      f1.inputValues();
      f2.inputValues();
    }

  }
}

Do you want the program to stop when either numerator or denominator is 0? Also why are you creating 2 objects of Fraction? — Nicholas K
– Nicholas K, Commented Feb 10, 2019 at 6:48
Well only numerator for now. I am creating 2 objects of Fraction as I want user to input 2 fractions in my program to add, multiply, divide etc. But for now, I can't even get it to loop until a 0 is being input. — ash
– ash, Commented Feb 10, 2019 at 6:53

Nicholas K · Accepted Answer · 2019-02-10 06:56:51Z

1

Well firstly your code doesn't compile. You need to return a value when the if condition evaluates to false, add the else condition to your isZero()

public boolean isZero() {
    if (getNumerator() == 0)
        return false;
    else
        return true;
}

Or a more cleaner way using ternary operator :

public boolean isZero() {
   return getNumerator() == 0 ? false: true;
}

Now you need just one object of the class Fraction

public static void main(String[] argv) {
    Fraction f1 = new Fraction();
    f1.inputValues();

    while (f1.isZero()) {
        f1.inputValues();
    }

}

Your program will now stop after the user enters 0 as the numerator.

edited Feb 10, 2019 at 6:56

answered Feb 10, 2019 at 6:51

Nicholas K

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Comments

Islam Hassan · Accepted Answer · 2019-02-10 06:51:43Z

0

First of all, your code won't compile. Methods that return a value must do so in all cases. Your isZero() method doesn't return true when it should. Modify it to the following:

public boolean isZero()
{
   if (getNumerator() == 0)
      return false;
   else 
      return true;
}

answered Feb 10, 2019 at 6:51

Islam Hassan

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Comments

Alvin X. · Accepted Answer · 2019-02-10 06:53:56Z

0

You should probably change your boolean

public boolean isZero() {

    if (getNumerator() == 0) {     //if is zero, return true, else, return false
        return true;
    } 
    return false;               //booleans default to false so you should return true when necessary
}

Syntactically, if you want the loop to continue while(true) change it to

 while (!f1.isZero()) {
        f1.inputValues();
 }

answered Feb 10, 2019 at 6:53

Alvin X.

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