Help with homework assignment

[J_5]

import java.util.Scanner;

public class Rational {
    private int numerator;
    private int denominator;

    public Rational() {
        numerator = 1;
        denominator = 2;
    }
    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;
    }
    public Rational add(Rational r) {
        int  num = numerator * r.denominator + r.numerator * denominator;
        int denom = denominator * r.denominator;
        return new Rational(num, denom);
    }
    public Rational subtract(Rational r) {
        int num = numerator * r.denominator - r.numerator * denominator;
        int denom = denominator  * r.denominator;
        return new Rational(num, denom);
    }
    public Rational multiply(Rational r) {
        int num = numerator * r.numerator;
        int denom = denominator * r.denominator;
        return  new Rational(num, denom);
    }
    public Rational divide(Rational r) {
        int num = numerator / r.numerator;
        int denom = denominator / r.denominator;
        return new Rational(num, denom);
    }
    public String toString() {
        return "(" + numerator + "/" + denominator + ")";
    }
}
class RationalTest {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        Rational a;
        Rational b;

        System.out.println("Enter numerator for the first rational number: ");
        int numa = input.nextInt();
        System.out.println("Enter a non-zero denominator for the first rational number: ");
        int denoma = input.nextInt();
        System.out.println("Enter a numerator for the second rational number: ");
        int numb = input.nextInt();
        System.out.println("Enter a non-zero denominator for the second rational number: ");
        int denomb = input.nextInt();

        a = new Rational(numa, denoma);
        b = new Rational(numb, denomb);

        System.out.println("First rational number is: " + a);
        System.out.println("Second rational number is: " + b);
        System.out.println("Addition of the rational number is: " + a.add(b));
        System.out.println("Subtraction of the rational number is: " + a.subtract(b));
        System.out.println("Multiplication of the rational number is: " + a.multiply(b));
        System.out.println("Division of the rational number is: " + a.divide(b));
    }
}

The insctructions say:
The constructor should store the fraction in reduced form.
a) Add two Rational numbers: The result of the addition should be stored in reduced
form.
b) Subtract two Rational numbers: The result of subtraction should be stored in reduced
form.
c) Multiply two Rational numbers: The result of the multiplication should be stored in
reduced form.
d) Divide two Rational numbers: The result of the division should be stored in reduced
form.
e) Return a String representation of Rational number in the form

[J_5]

A bit of clarification that i left out, i don't understand where to implement the reduction or how to use GCD in java

[JamesCherrill]

The constructor should store the fraction in reduced form.

So you should perform the reduction in the constructor.

Google Euclidean algorithm for a good way to compute the GCD