/**
 * A Class for implementing the data type fraction
 * Modified with accessor, mutator and helper methods
 * 
 * @author Mr J
 * @version 20040217
 */
public class NewFraction
{
	private int numerator;    // top part
	private int denominator;  // bottom part

	/**
	 * Constructor for objects of class Fraction
	 */
	public NewFraction()
	{
		// initialise instance variables
		setNumerator(0);
		setDenominator(1);
	}
	/**
	 * Construct a fraction given two ints (numerator first)
	 * 
	 * @param n the numerator
	 * @param d the denominator
	 * @throws FractionException
	 */
	public NewFraction(int n, int d) throws FractionException
	{
	    if (d != 0)
	    {
		  setNumerator(n);
		  setDenominator(d);
		}
		else
		{
		  throw new FractionException("Denominator can't be zero");
		}
	}

	/**
	 * A method to add two fractions
	 * 
	 * @param a a NewFraction
	 * @param b another NewFraction
	 * @return the sum of fractions a and b 
	 */
	public static NewFraction add(NewFraction a, NewFraction b) throws FractionException
	{
		// find the common denominator, multiply the numerators
		int cd = (a.denominator * b.denominator);
		a.numerator = a.numerator * b.denominator;
		b.numerator = b.numerator * a.denominator;
		// now add them
		int nm = a.numerator + b.numerator;
		
		// just return a new (simplified) fraction instance
        NewFraction newOne = new NewFraction(nm, cd);
        newOne.simplify();
        return newOne;
	}
	/**
	 * sets the numerator field
	 * 
	 * @param n top part of fraction
	 */
	public void setNumerator(int n)
	{
	    this.numerator = n;
	}
	/**
	 * sets the denominator field
	 * 
	 * @param d bottom part of fraction
	 */
	public void setDenominator(int d)
	{
	    this.denominator = d;
	}
	/**
	 * reduces fraction to lowest common denominator 
	 */
	public void simplify()
	{
	    int start = numerator;
	    boolean done = false;
	    while ( (!done) && (start > 1) )
	    {
	      // check that the numerator can be divided exactly by start
	      if (numerator%start == 0)
	      {
	          // see if the denominator can be divided exactly by the same number
	          if (denominator%start == 0)
	          {
	              // got a result
	              numerator = numerator / start;
	              denominator = denominator / start;
	              done = true;
	          }
	      }
	      start = start - 1;
	  }
	}
	/**
	 * Override toString() method of Class Object
	 * 
	 * @return a String representation of the Fraction 
	 */
	public String toString()
	{
	    return("" + numerator + "/" + denominator);
	}
}