Fraction and Calculator

Fraction.java

public class Fraction {    //Дробь
    public int denominator;  //Знаменатель
    public int numerator;  //Числитель

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

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

FractionCalculator.java

public class FractionCalculator {
    public Fraction add(Fraction first, Fraction second) { // принимает две дроби
        Fraction result = new Fraction(1, 1);
        if (first.denominator == second.denominator) { //если знаменатели одинаковые
            result.denominator = first.denominator;
            result.numerator = first.numerator + second.numerator;
        } else {
            int nok = nok(first.denominator, second.denominator);
            result.denominator = nok;
            result.numerator = first.numerator * (nok / first.denominator) + second.numerator * (nok / second.denominator);
        }
        return result;
    }

    public Fraction multiply(Fraction first, Fraction second) { // принимает две дроби
        Fraction result = new Fraction(1, 1);
        result.denominator = first.denominator * second.denominator;
        result.numerator = first.numerator * second.numerator;
        return result;
    }

    private int nod(int a, int b) {
        return b == 0 ? a : nod(b, a % b);
    }

    private int nok(int a, int b) {
        return a / nod(a, b) * b;
    }
}

FractionTest.java

public class FractionTest {
    public static void main(String[] args) {
        FractionCalculator calculator = new FractionCalculator(); // сначала создаем калькулятор

        Fraction frac1 = new Fraction(3, 4);
        Fraction frac2 = new Fraction(1, 5);
        Fraction sum = calculator.add(frac1, frac2);
        System.out.println(frac1 + " + " + frac2 +" = " + sum);

        Fraction mult = calculator.multiply(frac1, frac2);
        System.out.println(frac1 + " * " + frac2 +" = " + mult);
    }
}