Fraction

Fraction.java

public class Fraction {
	
	public static final Fraction ONE = new Fraction(1);
	public static final Fraction TWO = new Fraction(2);
	public static final Fraction TEN = new Fraction(10);
	
	private long num;
	private long denom;
	
	public Fraction(long num, long denom) {
		super();
		this.num = num;
		
		if (denom == 0) throw new Error("Cannot instantiate a fraction with 0 as denominator");
		
		this.denom = denom;
		
		simplify();
	}
	public Fraction(long num) {
		this(num, 1);
	}
	
	public Fraction multiply(Fraction val) {
		return new Fraction(num * val.num, denom * val.denom).simplify();
	}
	public Fraction divide(Fraction val) {
		return new Fraction(num * val.denom, denom * val.num).simplify();
	}
	public Fraction add(Fraction val) {
		return new Fraction(num * val.denom + val.num * denom, denom * val.denom).simplify();
	}
	public Fraction subtract(Fraction val) {
		return new Fraction(num * val.denom - val.num * denom, denom * val.denom).simplify();
	}
	
	public Fraction simplify() {
		long gcd = gcd(num, denom);
		num = num / gcd;
		denom = denom / gcd;
		return this;
	}
	
	private static long gcd(long a, long b) {
	    while (b > 0) {
	        long temp = b;
	        b = a % b;
	        a = temp;
	    }
	    return a;
	}
	
//	private static long lcm(long a, long b) {
//	    return a * (b / gcd(a, b));
//	}
	
	public double doubleValue() {
		return (double) num / denom;
	}
	
	@Override
	public String toString() {
		return num + "/" + denom;
	}
	
	@Override
	public boolean equals(Object obj) {
		if (!(obj instanceof Fraction))
			return false;
		Fraction that = (Fraction) obj;
		return ((long) num) * that.denom == ((long) that.num) * denom;
	}
}