Question

I'm having trouble with my ZeroDenominatorException. How do I implement it to where if the denominator is 0 it throws the ZeroDenominatorException and the catch catches to guarantee that the denominator is never 0.
/**
 * The main class is the driver for my Rational project.
 */
public class Main {

    /**
     * Main method is the entry point to my code.
     * @param args The command line arguments.
     */
    public static void main(String[] args) {

        int numerator, denominator = 0;

        System.out.println();

        try {

            Rational rad = new Rational(-1, 3);

            if (denominator == 0)
                throw new ZeroDenominatorException();

            else {
                System.out.println(rad);
            }
        }

        catch(ZeroDenominatorException e){

            System.err.println(e.getMessage());
        }
    }
}

import java.util.Objects;

public class Rational {

    private int numerator;
    private int denominator;

    public Rational(int numerator, int denominator) {
        this.numerator = numerator;
        this.denominator = denominator;
    }

    public int getNumerator() {
        return numerator;
    }

    public void setNumerator(int numerator) {
        this.numerator = numerator;
    }

    public int getDenominator() {
        return denominator;
    }

    public void setDenominator(int denominator) {
        this.denominator = denominator;
    }

    @Override
    public String toString() {
        boolean negative = (numerator < 0 || denominator < 0) && (numerator >= 0 || denominator > 0);
        int num = numerator, denum = denominator;
        if (num < 0)
            num = -num;
        if (denum < 0)
            denum = -denum;
        if (negative)
            return "-" + num + "/" + denum;
        else
            return num + "/" + denum;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Rational rational = (Rational) o;
        return numerator == rational.numerator &&
                denominator == rational.denominator;
    }

    @Override
    public int hashCode() {
        return Objects.hash(numerator, denominator);
    }
}

public class ZeroDenominatorException extends Exception {

    public ZeroDenominatorException(){

        super("The denominator cannot be zero!");
    }
}

Answer 1

/**
* The main class is the driver for my Rational project.
*/
public class Main {

/**
* Main method is the entry point to my code.
* @param args The command line arguments.
*/
public static void main(String[] args) {

int numerator=5;
int denominator = 0;
System.out.println();
try {
   Rational rad = new Rational(numerator,denominator);
   System.out.println(rad);
}
catch(ZeroDenominatorException e){

System.err.println(e.getMessage());
}
}
}

import java.util.Objects;

public class Rational {

private int numerator;
private int denominator;

public Rational(int numerator, int denominator) throws ZeroDenominatorException {
this.numerator = numerator;
this.setDenominator(denominator);
}

public int getNumerator() {
return numerator;
}

public void setNumerator(int numerator) {
this.numerator = numerator;
}

public int getDenominator() {
return denominator;
}

public void setDenominator(int denominator) throws ZeroDenominatorException {
   if(denominator==0){
       throw new ZeroDenominatorException();
   }
   else{
this.denominator = denominator;
   }
}

@Override
public String toString() {
boolean negative = (numerator < 0 || denominator < 0) && (numerator >= 0 || denominator > 0);
int num = numerator, denum = denominator;
if (num < 0)
num = -num;
if (denum < 0)
denum = -denum;
if (negative)
return "-" + num + "/" + denum;
else
return num + "/" + denum;
}

@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Rational rational = (Rational) o;
return numerator == rational.numerator &&
denominator == rational.denominator;
}

@Override
public int hashCode() {
return Objects.hash(numerator, denominator);
}
}

public class ZeroDenominatorException extends Exception {

public ZeroDenominatorException(){

super("The denominator cannot be zero!");
}
}

Expected output:

when numerator=5 and denominator =0

The denominator cannot be zero!

when numerator=5 and denominator=2

5/2