Fraction по схеме

import java.util.Objects;
 
public class Fraction implements Comparable<Fraction> {
    private long numerator;
    private long denominator;
 
    public Fraction(final long numerator, final long denominator) {
        this.numerator = numerator;
        this.denominator = denominator;
        if (denominator < 0) {
            this.numerator = -numerator;
            this.denominator = -denominator;
        }
 
        final long gcd = gcd(numerator, denominator);
        if (gcd != 1) {
            this.numerator /= gcd;
            this.denominator /= gcd;
        }
    }
 
    @Override
    public String toString() {
        return String.format("%d/%d", numerator, denominator);
    }
 
    public long getNumerator() {
        return numerator;
    }
 
    public void setNumerator(final long numerator) {
        this.numerator = numerator;
    }
 
    public long getDenominator() {
        return denominator;
    }
 
    public void setDenominator(final long denominator) {
        this.denominator = denominator;
    }
 
    @Override
    public boolean equals(final Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        final Fraction fraction = (Fraction) obj;
        return numerator == fraction.numerator &&
                denominator == fraction.denominator;
    }
 
    @Override
    public int hashCode() {
        return Objects.hash(numerator, denominator);
    }
 
    @Override
    public int compareTo(final Fraction f2) {
//        TODO:
        return 0;
    }
 
    public Fraction add(final Fraction fr) {
//        TODO:
        return null;
    }
 
    public Fraction sub(final Fraction fr) {
        return add(new Fraction(-fr.numerator, fr.denominator));
    }
 
    private long gcd(final long a, final long b) {
        return (b == 0 ? a : gcd(b, a % b));
    }
}

import junit.framework.Assert;
import org.junit.Test;
 
public class FractionTest {
    @Test
    public void test() {
        Assert.assertEquals(new Fraction(37, 40), new Fraction(1, 8).add(new Fraction(4, 5)));
        Assert.assertEquals(new Fraction(4, 9), new Fraction(24, 54));
        Assert.assertEquals("2/3", new Fraction(1, 5).add(new Fraction(7, 15)).toString());
        Assert.assertEquals("1/4", new Fraction(1, 1).sub(new Fraction(3, 4)).toString());
    }
}

return Long.compare(numerator * f2.denominator, f2.numerator * denominator)

return new Fraction(numerator * f2.denominator + f2.numerator * denominator, denominator * f2.denominator)