RationalWithMultipleConstructors.java

class Rational{
    private int numerator;
    private int denominator;

    int getNumerator() {
        return numerator;
    }

    int getDenominator() {
        return denominator;
    }

    Rational(int numerator, int denominator){
        int gcd = gcdByEuclidsAlgorithm(numerator, denominator);
        this.numerator = numerator / gcd;
        this.denominator = denominator / gcd;
    }

    Rational(int numerator){
        this(numerator, 1);
    }

    Rational(){
        this(1, 1);
    }

    public static void main(String[] args){
        Rational myRational = new Rational(20, 30);
        myRational.printRational("");
    }

    String printRational(String prefix){
        String rationalString = String.format("%s%d/%d", prefix, numerator, denominator);
        System.out.println(rationalString);
        return rationalString;
    }

    void negate(){
        numerator = -1 * numerator;
    }

    void invert(){
        int newDenominator = denominator;
        denominator = numerator;
        numerator = newDenominator;
    }

    double toDouble(){
        double numeratorDouble = numerator;
        double denominatorDouble = denominator;
        double fraction  = numeratorDouble/denominatorDouble;
        return fraction;
    }

    static int gcdByEuclidsAlgorithm(int n1, int n2) {
        if (n2 == 0) {
            return n1;
        }
        return gcdByEuclidsAlgorithm(n2, n1 % n2);
    }

    Rational addFraction(Rational fraction2){
        int numerator1 = this.numerator * fraction2.denominator;
        int numerator2 = fraction2.numerator * this.denominator;

        int denominator = this.denominator * fraction2.denominator;

        int newNumerator = numerator1 + numerator2;
        int newDenominator = denominator;

        return new Rational(newNumerator, newDenominator);
    }
}