Next: None. Up: Fraction class example. Previous: Coding.

Summary

This gives us the following complete class definition.

import csbsju.cs160.*;

public class Fraction {
    public static final Fraction ZERO = new Fraction(0, 1);
    public static final Fraction ONE = new Fraction(1, 1);

    private int num;
    private int den;

    public Fraction(int numerator, int denominator) {
        if(denominator < 0) {
            numerator *= -1;
            denominator *= -1;
        }

        int div = gcd(numerator, denominator);
        num = numerator / div;
        den = denominator / div;
    }

    private static int gcd(int a, int b) {
        while(b != 0) {
            int r = a % b;
            a = b;
            b = r;
        }
        return a;
    }

    public double doubleValue() {
        return (num + 0.0) / den;
    }

    public Fraction add(Fraction other) {
        return new Fraction(num * other.den + den * other.num,
            den * other.den);
    }

    public Fraction multiply(Fraction other) {
        return new Fraction(num * other.num, den * other.den);
    }

    public int compareTo(Fraction other) {
        // first check if they are equal
        if(num == other.num && den == other.den) return 0;

        // otherwise see which is less
        int first = num * other.den;
        int second = other.num * den;
        if(first < second) return -1;
        else return 1;
    }

    public String toString() {
        if(den == 1) {
            return "" + num;
        } else {
            return num + "/" + den;
        }
    }

    public static Fraction parseFraction(String str) {
        int numer; // numerator of new fraction
        int denom; // denominator of new fraction

        int slash = str.indexOf("/");
        if(slash < 0) { // the string contains only an integer
            numer = Integer.parseInt(str);
            denom = 1;
        } else {
            numer = Integer.parseInt(str.substring(0, slash));
            denom = Integer.parseInt(str.substring(slash + 1));
        }

        return new Fraction(numer, denom);
    }
}

Exercise

Next: None. Up: Fraction class example. Previous: Summary.