Rational Class - Unable to Reduce fraction and Divide

Question

My Rational Class is supposed to add, subtract, multiply, and divide fractions so when called in the Main Class, it will perform these actions. However, I can't seem to reduce my fractions (gcd) properly to get the right answer and the division method isn't running at all (I get a error message):

Exception in thread "main" java.lang.ArithmeticException: / by zero at Rational.division(Project1.java:45) at Project1.main(Project1.java:12)

How can I fix these problems? Thanks

public class Project1 {

public static void main(String[] args) {

    Rational a = new Rational (6, 12);
    Rational b = new Rational (8, 9);

    System.out.println(a + " + " + b + " = " + a.add(b));
    System.out.println(a + " - " + b + " = " + a.subtraction(b));
    System.out.println(a + " * " + b + " = " + a.multiply(b));
    System.out.println(a + " / " + b + " = " + a.division(b));
}

}

class Rational {

private int numerator, denominator;

public Rational(int num, int denom) {
    numerator = num;
    denominator = denom;
}
public Rational gcd() {
    while (numerator != denominator)
    {
        if (numerator > denominator)
            numerator = numerator - denominator;
        else
            denominator = denominator - numerator;
    }
    return new Rational(numerator, denominator);
}

public Rational add(Rational o) {
    return new Rational (numerator + o.numerator, denominator +o.denominator);
}

public Rational conjugate() {
    return new Rational (numerator, - denominator);
}

public Rational division(Rational o) {
    return new Rational ((numerator/denominator) / (numerator/denominator), denominator);
}

public Rational multiply(Rational o) {
    return new Rational (numerator * o.numerator, denominator * o.denominator);
}

public Rational subtraction(Rational o) {
    return new Rational (numerator - o.numerator, denominator - o.denominator);
}

public String toString() {
    return (numerator + "/" + denominator);
}

}

that's not how you add fractions – zedling Mar 21 '19 at 22:07 — zedling, Mar 21 '19 at 22:07

score 1 · Answer 1 · answered Oct 20 '16 at 17:41

The problem you have is here:

public Rational division(Rational o) {
    return new Rational ((numerator/denominator) / (numerator/denominator), denominator);
}

When you run your code you do:

(6/12)/(6/12)

Both (6/12) 's in the brackets are downcasted to 0, and hence you end up diving by 0 which isn't allowed.

I'd recommend debugging code with System.out.println() to see where you go wrong. But the error is pretty clear, you're dividing by 0.

score 0 · Answer 2 · answered Oct 20 '16 at 17:43

I would change the logic in your division method. You don't really even need to divide to calculate a fraction, which would avoid the situation where you are dividing by zero. Instead I would do this to divide two fractions:

return new Rational (numerator * o.denominator, o.numerator * denominator);

Also I don't really follow the logic in your GCD function, as I'm guessing this is causing you an infinite loop. Look up Euclid's algorithm if you need some help.

score 0 · Answer 3 · answered Oct 20 '16 at 17:45

0

private int numerator, denominator;//this value is 0

the same you are using in

public Rational division(Rational o) {
    return new Rational ((numerator/denominator) / (numerator/denominator), denominator);
}

instead of object o

answered Oct 20 '16 at 17:45

Shreyas Sarvothama

486
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Rational Class - Unable to Reduce fraction and Divide

3 Answers3