The Rational class with unlimited numbers to process

BigIntegerRational.java

class Rational extends Number implements Comparable<Rational> {
    
    // Data fields for numerator and denominator
    private BigInteger numerator = BigInteger.ZERO;
    private BigInteger denominator = BigInteger.ONE;
    
    /** Construct a rational with default properties */
    public Rational() {
        this(BigInteger.ZERO, BigInteger.ONE);
    }
    
    /** Construct a rational with specified numerator and denominator
     * @param numerator the numerator
     * @param denominator the denominator
     */
    public Rational (BigInteger numerator, BigInteger denominator) {
        BigInteger gcd = gcd(numerator, denominator);
        
        this.numerator = (denominator.compareTo(BigInteger.ZERO) == 1? 
                BigInteger.ONE : new BigInteger("-1"))
                .multiply(numerator).divide(gcd);
        
        this.denominator = denominator.abs().divide(gcd);
    }
    
    /** Find two GCD for two numbers */
    private static BigInteger gcd(BigInteger n, BigInteger d) {
        BigInteger n1 = n.abs();
        BigInteger n2 = d.abs();
        BigInteger gcd = BigInteger.ONE;
        
        for    (
                BigInteger k = BigInteger.ONE;
                n1.compareTo(k) < 1 && n2.compareTo(k) < 1;
                k.add(BigInteger.ONE)) {
            
            if (n1.remainder(k).equals(BigInteger.ZERO) && 
                    n2.remainder(k).equals(BigInteger.ZERO))
                gcd = k;
        }
        
        return gcd;
    }

    /** 
     * Get the numerator
     * @return the numerator
     */
    public BigInteger getNumerator() {
        return numerator;
    }

    /**
     * Get the denominator
     * @return the denominator
     */
    public BigInteger getDenominator() {
        return denominator;
    }
    
    /** 
     * Add a rational number to this rational
     * @param sec the added rational
     * @return the new rational after the adding
     */
    public Rational add(Rational sec) {
        BigInteger newNumerator = 
                numerator.multiply(sec.denominator).
                add(sec.getNumerator().multiply(denominator));
        
        BigInteger newDenomenator = denominator.multiply(sec.denominator);
        
        return new Rational(newNumerator, newDenomenator);
    }
    
    /**
     * Subtract a rational from this rational
     * @param sec the subtracted rational
     * @return the new rational after the subtraction
     */
    public Rational subtract(Rational sec) {
        
        BigInteger newNumerator = 
                numerator.multiply(sec.denominator).
                subtract(sec.numerator.multiply(denominator));
        
        BigInteger newDenomenator = denominator.multiply(sec.denominator);
        
        return new Rational(newNumerator, newDenomenator);
    }
    
    /** 
     * Multiply a rational number by this rational
     * @param sec the multiplied rational
     * @return the new rational after the multiplying
     */
    public Rational multiply(Rational sec) {
        BigInteger newNumerator = numerator.multiply(sec.numerator);
        BigInteger newDenomenator = denominator.multiply(sec.denominator);
        
        return new Rational(newNumerator, newDenomenator);
    }
    
    /** 
     * Divide a rational number by this rational
     * @param secondRational the divided rational
     * @return the new rational after the dividing
     */
    public Rational divide(Rational sec) {
        BigInteger newNumerator = numerator.multiply(sec.denominator);
        BigInteger newDenomenator = denominator.multiply(sec.numerator);
        
        return new Rational(newNumerator, newDenomenator);
    }
    
    @Override
    public String toString() {
        if (denominator.equals(BigInteger.ONE))
            return numerator.toString();
        else
            return numerator + "/" + denominator;
    }
    
    
    @Override
    public boolean equals(Object o) {
        return this.subtract((Rational) o).getNumerator().equals(BigInteger.ONE);
    }
    
    // Implement the intValue method in Number
    @Override
    public int intValue() {
        return (int) doubleValue();
    }
    
    // Implement the floatValue method in Number
    @Override
    public float floatValue() {
        return (float) doubleValue();
    }
    
    // Implement the doubleValue method in Number
    @Override 
    public double doubleValue() {
        return numerator.doubleValue() * 1.0 / denominator.doubleValue();
    }
    
    // Implement the loneValue method in Number
    @Override
    public long longValue() {
        return (long) doubleValue();
    }
    
    @Override
    public int compareTo(Rational sec) {
        BigInteger n = this.subtract((Rational) sec).getNumerator();
        if (n.compareTo(BigInteger.ZERO) > 0) {
            return 1;
        } else if (n.compareTo(BigInteger.ZERO) < 0) {
            return -1;
        } else {
            return 0;
        }
    }
}