Fraction.java

/*
 * f1 = Fraction(1,2)
 * class Fraction:
 * 	__init__(self, numerator, denominator):
 *   self.numerator = numerator
 *   self.denominator = denominator
 */
public class Fraction 
{
	//fields - variables associated with a class
	long numerator;
	long denominator;
	
	//constructor
	public Fraction(long numerator, long denominator)
	{
		this.numerator = numerator;
		this.denominator = denominator;
	}
	
	public Fraction(String f)
	{
		//f is in the format of "numerator/denominator" so
		//somehow (using only what we have learned in class)
		//divide the string and set the numerator and denominator
		String numString = "";
		int pos = 0;
		while(f.charAt(pos) != '/')
		{
			numString = numString + f.charAt(pos);
			pos = pos + 1;
		}
		
		pos = pos + 1; //skips past the /
		String denomString = "";
		while(pos < f.length())
		{
			denomString = denomString + f.charAt(pos);
			pos = pos + 1;
		}
		this.numerator = this.stringToInt(numString);
		this.denominator = this.stringToInt(denomString);
	}
	
	static Fraction buildFraction(long numerator, long denominator)
	{
		return new Fraction(numerator, denominator);
	}
	
	//methods
	public Fraction add(Fraction f)
	{
		//adds f to "this" Fraction and returns
		//a new Fraction object that is the sum
		//of the two
		long denom = this.denominator * f.denominator;
		long num = (this.denominator * f.numerator) + 
				(f.denominator * this.numerator);
		Fraction answer = new Fraction(num, denom);
		return answer;
	}
	
	public void reduceEuclidean()
	{
		long a = this.numerator;
		long b = this.denominator;
		long t;
		while(b != 0)
		{
			t = b;
			b = a % b;
			a = t;
		}
		//a is now our GCD of numerator and denominator
		this.numerator = this.numerator / a;
		this.denominator = this.denominator / a;
	}
	
	public void reduce()
	{
		long smallest = this.numerator;
		if(this.denominator < smallest)
		{
			smallest = this.denominator;
		}
		//smallest is the smaller of the 2 numbers
		//Find the GCD (Greatest Common Divisor)
		while(smallest >= 1)
		{
			if(this.numerator % smallest == 0 &&
					this.denominator % smallest == 0)
			{
				//we have found the GCD, it is smallest
				this.numerator = this.numerator / smallest;
				this.denominator = this.denominator / smallest;
				return; //I have found and applied the GCD, so kill the method
			}
			else
			{
				smallest = smallest - 1;
			}
		}
	}
	
	private int stringToInt(String dec)
	{
		int sum = 0;
		int place = 1;
		String map = "0123456789";
		for(int i = dec.length()-1; i >= 0; i = i - 1)
		{
			sum = sum + (place * map.indexOf(dec.charAt(i)));
			place = place * 10;
		}
		return sum;
	}
	//this overrides the default toString method we inherited
	//from the Object class and allows us to do our own thing
	//historic function - returns a value
	public String toString()
	{
		return this.numerator + "/" + this.denominator;
	}
	
	//historic procedure - does NOT return a value
	public void display()
	{
		
		System.out.println(this.numerator + "/" + this.denominator);
	}
	
}