Rational.java

public class Rational extends Number implements Comparable<Rational> {

    /**
     *
     */
    private static final long serialVersionUID = 1L;

    private static final int kCFLLength = 16;

    private final long mN, mD;

    private static long gcd(long a, long b) {
        return (b == 0) ? a : gcd(b, a % b);
    }

    public Rational(long n, long d) {
        if(d == 0) {
            throw new RuntimeException("Division By 0!");
        }

        long factor = gcd(Math.abs(n), Math.abs(d));
        mN = (n / factor) * ((d < 0) ? -1 : 1);
        mD = (Math.abs(d) / factor); 
    }

    public Rational(Rational other) {
        this(other.getNumerator(), other.getDenominator());
    }

    public Rational(double num) {
        // Continued fraction list
        long[] cfl = new long[kCFLLength];
        long cflMax = 0;
        int iter = kCFLLength - 1;

        // Store the sign of the original number
        long sign = (long)(Math.signum(num));
        num = Math.abs(num);

        // Calculate continued fraction list
        for(int i = 0; i < cfl.length; ++i) {
            cfl[i] = (long)(Math.floor(num));
            num -= cfl[i];
            
            if(num != 0) {
                num = Math.abs(1.0 / num);
            } else {
                iter = i;
                break;
            }

            if(cfl[i] >= cflMax) {
                cflMax = cfl[i];
                iter = i;
            }
        }

        // Calculate numerator and denominator
        long n = 0, d = 1;
        for(int i = iter; i >= 0; --i) {
            long t = cfl[i] * n + d;
            d = n;
            n = t;
        }

        long factor = gcd(Math.abs(n), Math.abs(d));
        mN = (n / factor) * ((d < 0) ? -1 : 1) * sign;
        mD = (Math.abs(d) / factor); 
    }

    public Rational(long num) {
	    this(num, 1);
    }
    
    public long getNumerator() {
        return mN;
    }

    public long getDenominator() {
        return mD;
    }

    public Rational add(Rational other) {
        long n_a = this.getNumerator() * other.getDenominator();
        long n_b = other.getNumerator() * this.getDenominator();
        long d = this.getDenominator() * other.getDenominator();
        return new Rational(n_a + n_b, d);
    }

    public Rational sub(Rational other) {
        long n_a = this.getNumerator() * other.getDenominator();
        long n_b = other.getNumerator() * this.getDenominator();
        long d = this.getDenominator() * other.getDenominator();
        return new Rational(n_a - n_b, d);
    }

    public Rational mul(Rational other) {
        return new Rational(this.getNumerator() * other.getNumerator(), this.getDenominator() * other.getDenominator());
    }

    public Rational div(Rational other) {
        return new Rational(this.getNumerator() * other.getDenominator(), this.getDenominator() * other.getNumerator());
    }

    @Override
    public int intValue() {
        return ((int) mN) / ((int) mD);
    }
    
    @Override
    public long longValue() {
        return ((long) mN) / ((long) mD);
    }
    
    @Override
    public float floatValue() {
        return ((float) mN) / ((float) mD);
    }

    @Override
    public double doubleValue() {
        return ((double) mN) / ((double) mD);
    }

    @Override
    public int compareTo(Rational other) {
        long n_a = this.getNumerator() * other.getDenominator();
        long n_b = other.getNumerator() * this.getDenominator();
        
        return (int)(Math.signum(n_a - n_b));
    }

    @Override
    public String toString() {
        return "[" + mN + " / " + mD + "]";
    }

    public static void main(String[] args) {
        Rational a = new Rational(Math.sqrt(2));
        Rational b = new Rational(Math.E);

        System.out.println("a: " + a.doubleValue());
        System.out.println("b: " + b.doubleValue());
        System.out.println("a: " + a);
        System.out.println("b: " + b);
        System.out.println("a + b: " + a.add(b));
        System.out.println("a - b: " + a.sub(b));
        System.out.println("a * b: " + a.mul(b));
        System.out.println("a / b: " + a.div(b));
    }
}