Question

public class Rational
{
    // PUT PRIVATE DATA FIELDS HERE

    /**
     * The default constructor for objects of class Rational.  Creates the rational number 1.
     */
    public Rational()
    {       
        // ADD CODE TO THE CONSTRUCTOR
    }

    /**
     * The alternate constructor for objects of class Rational.  Creates a rational number equivalent to n/d.
     * @param n The numerator of the rational number.
     * @param d The denominator of the rational number.
     */    
    public Rational(int n, int d)
    {
        // ADD CODE TO THE ALTERNATE CONSTRUCTOR
    }
    
    /**
     * Get the value of the Numerator
     *
     * @return     the value of the numerator
     */
    public int getNumerator()
    {
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return 0;
    }
    
    /**
     * Get the value of the Denominator
     *
     * @return     the value of the denominator
     */
    public int getDenominator()
    {
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return 0;
    }


    /**
     * Negate a rational number r
     * 
     * @return a new rational number that is negation of this number -r
     */    
    public Rational negate()
    {               
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }


    /**
     * Invert a rational number r 
     * 
     * @return a new rational number that is 1/r.
     */    
    public Rational invert()
    {               
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }





    /**
     * Add two rational numbers
     *
     * @param other the second argument of the add
     * @return a new rational number that is the sum of this and the other rational
     */    
    public Rational add(Rational other)
    {       
        // ADD NEW CODE AND CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }
    
     /**
     * Subtract a rational number t from this one r
     *
     * @param other the second argument of subtract
     * @return a new rational number that is r-t
     */    
    public Rational subtract(Rational other)
    {               
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }

    /**
     * Multiply two rational numbers
     *
     * @param other the second argument of multiply
     * @return a new rational number that is the sum of this object and the other rational.
     */    
    public Rational multiply(Rational other)
    {       
        // ADD NEW CODE AND CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }
        
 
     /**
     * Divide this rational number r by another one t
     *
     * @param other the second argument of divide
     * @return a new rational number that is r/t
     */    
    public Rational divide(Rational other)
    {               
        // CHANGE THE RETURN TO SOMETHING APPROPRIATE
        return null;
    }
     
 
 
 /**
     * Put the rational number in normal form where the numerator
     * and the denominator share no common factors.  Guarantee that only the numerator
     * is negative.
     *
     */
    private void normalize()
    {
        // ADD CODE TO NORMALIZE THE RATIONAL NUMBER
    }
    
    /**
     * Recursively compute the greatest common divisor of two positive integers
     *
     * @param a the first argument of gcd
     * @param b the second argument of gcd
     * @return the gcd of the two arguments
     */
    private int gcd(int a, int b)
    {
        int result = 0;
        if(a<b)
            result = gcd(b,a);
        else if(b==0)
            result = a;
        else
        {
            int remainder = a % b;
            result = gcd(b, remainder);
        }
        return result;
    }
   
    
    
}

Answer 1

class Rational
{
// PUT PRIVATE DATA FIELDS HERE
private int numerator;
private int denominator;

/**
* The default constructor for objects of class Rational. Creates the rational number 1.
*/
public Rational()
{   
// ADD CODE TO THE CONSTRUCTOR
numerator = 0;
denominator = 1;
}

/**
* The alternate constructor for objects of class Rational. Creates a rational number equivalent to n/d.
* @param n The numerator of the rational number.
* @param d The denominator of the rational number.
*/
public Rational(int n, int d)
{
// ADD CODE TO THE ALTERNATE CONSTRUCTOR
numerator = n;
denominator = d;
}
  
/**
* Get the value of the Numerator
*
* @return the value of the numerator
*/
public int getNumerator()
{
// CHANGE THE RETURN TO SOMETHING APPROPRIATE
return numerator;
  
}
  
/**
* Get the value of the Denominator
*
* @return the value of the denominator
*/
public int getDenominator()
{
// CHANGE THE RETURN TO SOMETHING APPROPRIATE
return denominator;
  
}

/**
* Negate a rational number r
*
* @return a new rational number that is negation of this number -r
*/
public Rational negate()
{   
// CHANGE THE RETURN TO SOMETHING APPROPRIATE
  
return new Rational(-this.numerator,this.denominator);
}

/**
* Invert a rational number r
*
* @return a new rational number that is 1/r.
*/
public Rational invert()
{   
// CHANGE THE RETURN TO SOMETHING APPROPRIATE
int temp = numerator;
numerator = denominator;
denominator = temp;
return new Rational(numerator,denominator);
}

/**
* Add two rational numbers
*
* @param other the second argument of the add
* @return a new rational number that is the sum of this and the other rational
*/
public Rational add(Rational other)
{   
// ADD NEW CODE AND CHANGE THE RETURN TO SOMETHING APPROPRIATE

       int num, den;
       den = denominator * other.getDenominator();
       num = numerator * other.getDenominator() +other.getNumerator() * denominator;
       Rational r = new Rational (num, den);
       r.normalize();
       return r;
  
  
}
  
/**
* Subtract a rational number t from this one r
*
* @param other the second argument of subtract
* @return a new rational number that is r-t
*/
public Rational subtract(Rational other)
{   
// CHANGE THE RETURN TO SOMETHING APPROPRIATE

       int num, den;
       den = denominator * other.getDenominator();
       num = numerator * other.getDenominator() - other.getNumerator() * denominator;
       Rational r = new Rational (num, den);
       r.normalize();
       return r;
}

/**
* Multiply two rational numbers
*
* @param other the second argument of multiply
* @return a new rational number that is the sum of this object and the other rational.
*/
public Rational multiply(Rational other)
{   
// ADD NEW CODE AND CHANGE THE RETURN TO SOMETHING APPROPRIATE

       int num, den;
       den = denominator * other.getDenominator();
       num = numerator * other.getNumerator();
       Rational r = new Rational (num, den);
       r.normalize();
       return r;
}
  

/**
* Divide this rational number r by another one t
*
* @param other the second argument of divide
* @return a new rational number that is r/t
*/
public Rational divide(Rational other)
{   
// CHANGE THE RETURN TO SOMETHING APPROPRIATE
  
       int num, den;
       den = denominator * other.getNumerator();
       num = numerator * other.getDenominator();
       Rational r = new Rational (num, den);
       r.normalize();
       return r;
}



/**
* Put the rational number in normal form where the numerator
* and the denominator share no common factors. Guarantee that only the numerator
* is negative.
*
*/
private void normalize()
{
// ADD CODE TO NORMALIZE THE RATIONAL NUMBER
int factor;
       factor = gcd(numerator, denominator);
       numerator = numerator / factor;
       denominator = denominator / factor;
}
  
/**
* Recursively compute the greatest common divisor of two positive integers
*
* @param a the first argument of gcd
* @param b the second argument of gcd
* @return the gcd of the two arguments
*/
private int gcd(int a, int b)
{
int result = 0;
if(a<b)
result = gcd(b,a);
else if(b==0)
result = a;
else
{
int remainder = a % b;
result = gcd(b, remainder);
}
return result;
}

  
  
}
class RationalTest
{
   public static void main (String[] args)
   {
       Rational r1 = new Rational(4,5);
       Rational r2 = new Rational(3,4);
      
       Rational sum = new Rational();
       sum = r1.add(r2);
      
       System.out.println(" Sum of r1 and r2 = "+sum.getNumerator()+"/"+sum.getDenominator());
      
       Rational sub = new Rational();
       sub = r1.subtract(r2);
      
       System.out.println(" Subtraction of r2 from r1 = "+sub.getNumerator()+"/"+sub.getDenominator());
      
       Rational mul = new Rational();
       mul = r1.multiply(r2);
      
       System.out.println(" Multiplication of r1 and r2 = "+mul.getNumerator()+"/"+mul.getDenominator());
      
       Rational div = new Rational();
       div = r1.divide(r2);
      
       System.out.println(" Division of r1 and r2 = "+div.getNumerator()+"/"+div.getDenominator());
      
       Rational inv = new Rational();
       inv = r1.invert();
       System.out.println("Inverse of r1 : "+inv.getNumerator()+"/"+inv.getDenominator());
      
       Rational neg = new Rational();
       neg = r2.negate();
       System.out.println("Negation of r2 : "+neg.getNumerator()+"/"+neg.getDenominator());
   }
}

Output:

 Sum of r1 and r2 = 31/20
 Subtraction of r2 from r1 = 1/20
 Multiplication of r1 and r2 = 3/5
 Division of r1 and r2 = 16/15
Inverse of r1 : 5/4
Negation of r2 : -3/4

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