/** *********************************************************
 *  FractClass implements a Fraction ADT.<BR>
 *  <B>Integrity Constraint:</B> The object's value is the<BR>
 *  correct value of the last fraction Stored or computed.
 *  @author Jeff Offutt
 *  @version 1.2, 1/99
********************************************************* **/

public class FractClass
{

// Class variables
   private static int CurNumFracs = 0;

// Class methods
/** *********************************************************
 * Class Method : Returns the current number of fractions <BR>
 * pre: null <BR>
 * post: null
 * @param None
 * @return An integer, the current number of fractions
********************************************************* **/
public static int GetNumFracs ()
{
   return (CurNumFracs);
}

// Public constructor methods ///////////////////////////////
/** *********************************************************
 * Constructor : Sets fraction to 0/1 <BR>
 * pre: null <BR>
 * post: fraction's value is 0/1; number of fractions is incremented
 * @param None
 * @return None
********************************************************* **/
public FractClass () //constructor
{
   Numerator   = 0;
   Denominator = 1;
   CurNumFracs++;
}

/** *********************************************************
 * Constructor : Initialize a new fraction with supplied values <BR>
 * pre: Den is not 0 <BR>
 * post: fraction's value is Num/Den; number of fractions is incremented
 * @param Num Integer numerator
 * @param Den Integer denominator
 * @return None
********************************************************* **/
public FractClass (int Num, int Den) //constructor
{
   Numerator   = Num;
   Denominator = Den;
   CurNumFracs++;
}

// Public mutator methods ///////////////////////////////////
/** *********************************************************
 * Mutator : Adds two fractions, F1 = F1+F2<BR>
 * pre: Both denominators must be the same<BR>
 * (checked with the exception ArithmeticException) <BR>
 * post: Object's value is old-value+Right
 * @param Right FractClass right-hand-side
 * @return None
********************************************************* **/
public void Add (FractClass Right)
{
   try
   {
      Numerator = Numerator + Right.Numerator;
      if (Denominator != Right.Denominator)
         throw new ArithmeticException ();
   }
   catch (ArithmeticException e)
   {
      System.out.println ("Fraction add error: Denominators must be the same.");
   }
}

/** *********************************************************
 * Mutator : Multiplies two fractions, F1 = F1*F2 <BR>
 * pre: null <BR>
 * post: Object's value is old-value*Right
 * @param Right FractClass right-hand-side
 * @return None
********************************************************* **/
public void Mult (FractClass Right)
{
   Numerator   = Numerator   * Right.Numerator;
   Denominator = Denominator * Right.Denominator;
}

// Public accessor methods //////////////////////////////////
/** *********************************************************
 * Accessor : Compares two fractions for equality <BR>
 * pre: null <BR>
 * post: null
 * @param Right FractClass right-hand-side
 * @return boolean (F1 == F2)
********************************************************* **/
public boolean equals (Object Right)
{
   if (!(Right instanceof FractClass))
      return (false);
   FractClass rhs = (FractClass) Right;
   if (Numerator == rhs.Numerator && Denominator == rhs.Denominator)
      return (true);
   else
      return (false);
}

/** *********************************************************
 * Accessor : Prints a fraction using println <BR>
 * pre: null <BR>
 * post: Fraction is printed
 * @param None
 * @return None
********************************************************* **/
public void PrintFrac ()
{
   System.out.println (Numerator + " / " + Denominator);
}

/** *********************************************************
 * Accessor : Converts a fraction to a string for println <BR>
 * pre: null <BR>
 * post: null
 * @param None
 * @return String representation of the value is returned
********************************************************* **/
public String toString ()
{
   return (Numerator + " / " + Denominator);
}

/** *********************************************************
 * Main program function, tests the ADT class
 * @param None
 * @return None
********************************************************* **/
public static void main (String argv[])
{
   FractClass f1, f2, f3, f4, f5;

   System.out.println ("Instances: " + FractClass.GetNumFracs ());

   f1 = new FractClass (1, 2);
   f2 = new FractClass (3, 4);
   f3 = new FractClass (2, 4);
   f4 = new FractClass ();

   System.out.println ("Instances: " + FractClass.GetNumFracs ());

   System.out.print ("f1: ");
   f1.PrintFrac ();
   System.out.print ("f2: ");
   f2.PrintFrac ();
   System.out.print ("f3: ");
   f3.PrintFrac ();
   System.out.print ("f4: ");
   f4.PrintFrac ();

   f2.Add (f3);
   System.out.print ("f2: ");
   f2.PrintFrac ();
   f1.Mult (f3);
   System.out.print ("f1: ");
   f1.PrintFrac ();

   System.out.println ("Instances: " + FractClass.GetNumFracs ());

   System.out.print ("f1: ");
   System.out.println (f1);  // Implicit call to f1.toString()

   f5 = new FractClass (2, 4);
   System.out.print ("f5: ");
   System.out.println (f5);
   if (f3 == f5)
      System.out.println ("f3 and f5 are the same.");
   else
      System.out.println ("f3 and f5 are not the same.");

   if (f3.equals (f5))
      System.out.println ("f3 and f5 have the same values.");
   else
      System.out.println ("f3 and f5 do not have the same values.");

   if (f4.equals (f5))
      System.out.println ("f4 and f5 have the same values.");
   else
      System.out.println ("f4 and f5 do not have the same values.");

   f1.Add (f5);
   System.out.print ("f1: ");
   f1.PrintFrac ();
}  // end main

/////////////////////////////////////////////////////////////
//  Instance variables.                                    // 
/////////////////////////////////////////////////////////////

   private int Numerator;
   private int Denominator;
} // End FractClass