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There is a newer version: 0.0.13
package uk.co.codera.lang.math;

import java.math.BigInteger;

import org.apache.commons.lang3.builder.EqualsBuilder;
import org.apache.commons.lang3.builder.HashCodeBuilder;

public class Fraction {

    private final int nominator;
    private final int denominator;

    private Fraction(int nominator, int denominator) {
        int gcd = gcd(nominator, denominator);
        this.nominator = nominator / gcd;
        this.denominator = denominator / gcd;
    }

    public static Fraction from(String fraction) {
        String[] split = fraction.split("/");
        return from(Integer.valueOf(split[0]), Integer.parseInt(split[1]));
    }

    public static Fraction from(int nominator, int denominator) {
        return new Fraction(nominator, denominator);
    }

    public Fraction reciprocal() {
        return from(Integer.signum(this.nominator) * this.denominator, Integer.signum(this.nominator) * this.nominator);
    }

    public Fraction multiply(Fraction other) {
        return from(this.nominator * other.nominator, this.denominator * other.denominator);
    }

    public Fraction add(Fraction other) {
        return from((this.nominator * other.denominator) + (other.nominator * this.denominator), this.denominator
                * other.denominator);
    }

    public Fraction subtract(Fraction other) {
        return from((this.nominator * other.denominator) - (other.nominator * this.denominator), this.denominator
                * other.denominator);
    }

    public Fraction divide(Fraction other) {
        return this.multiply(other.reciprocal());
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder().append(this.nominator).append(this.denominator).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (!(obj instanceof Fraction)) {
            return false;
        }
        Fraction other = (Fraction) obj;
        return new EqualsBuilder().append(this.nominator, other.nominator).append(this.denominator, other.denominator)
                .isEquals();
    }

    @Override
    public String toString() {
        return this.nominator + "/" + this.denominator;
    }

    private int gcd(int nominator, int denominator) {
        return BigInteger.valueOf(nominator).gcd(BigInteger.valueOf(denominator)).intValue();
    }
}