The Rational class is used for rational number. A rational number consists of a numerator and a denominator. There are many equivalent rational numbers—for example, 1/3 = 2/6 = 3/9 = 4/12. The numerator and the denominator of 1/3 have no common divisor except 1

Rational.java

/**
 * The {@link Rational} class is used for rational number.
 * A rational number consists of a numerator and a denominator. 
 * There are many equivalent rational numbers—for example, 
 * 1/3 = 2/6 = 3/9 = 4/12. 
 * The numerator and the denominator of 1/3 have no common divisor except 1
 * 
 * @author AhmedNasser
 */
public class Rational extends Number implements Comparable<Rational> {
    
    
    
    // Data fields for numerator and denominator
    private long numerator = 0;
    private long denominator = 1;
    
    /** Construct a rational with default properties */
    public Rational() {
        this(0, 1);
    }
    
    /** Construct a rational with specified numerator and denominator
     * @param numerator the numerator
     * @param denominator the denominator
     */
    public Rational (long numerator, long denominator) {
        int gcd = gcd(numerator, denominator);
        this.numerator = ((denominator > 0 ? 1 : -1) * numerator / gcd);
        this.denominator = Math.abs(denominator) / gcd;
    }
    
    /** Find two GCD for two numbers */
    private static int gcd(long n, long d) {
        long n1 = Math.abs(n);
        long n2 = Math.abs(d);
        
        int gcd = 1;
        
        for (int k = 1; k <= n1 && k <= n2; k++)
            if (n1 % k == 0 && n2 % k == 0)
                gcd = k;
        
        return gcd;
    }

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

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