Very new to Java - HELP

[Jobie111]

Hello,

First off, thank you to anyone who helps me in advance. I am about as new as one can be to Java, and am having some troubles. In the below code, the goal is to create a fraction. The rules are the denominator has to remain positive and I have to reduce the fraction with its greatest common denominator. The "private static inc common" part was supplied and has to be used. The problem I am having is that when I test it, the denominator is not being made positive by multiplying by -1, and the fraction is not being reduced (i.e. when I add 1/-2 and 1/4 I am getting 2/-8 instead of -1/4. Also, the runtime error will not compile (which is why it is commented out), and I don't know why.

public class Fraction
{

	private int top, bottom;

	public Fraction(int numerator, int denominator) {
	top = numerator;
	bottom = denominator;

	//if (bottom == 0);
				//throw new RuntimeError("Attempt to create zero denominator fraction");
	}

	public int getTop() {
		return top;
	}

	public int getBottom() {
		return bottom;
	}

	

	private void reduce() {
	
		if (bottom < 0)
		{
			top *= -1;
			bottom *= -1;
		}
		
		int factor = common(top,bottom);
		top = top/factor;
		bottom = bottom/factor;
	}

	private static int common(int x, int y) { 
    if ( y == 0 ) return x;
    else return common(y, x%y);
    }


	public Fraction plus(Fraction f) {
		int num1 = top;
		int num2 = f.top;
		int denom1 = bottom;
		int denom2 = f.bottom;

		int newNum = (num1 * denom2) + (num2 * denom1);
		int newDenom = (denom1 * denom2);
		
		return new Fraction(newNum, newDenom);
	}

	public Fraction minus(Fraction f) {
		int num1 = top();
		int num2 = f.top();
		int denom1 = bottom();
		int denom2 = f.bottom();

		int newNum = (num1 * denom2) - (num2 * denom1);
		int newDenom = (denom1 * denom2);

		return new Fraction(newNum, newDenom);
	}

	public Fraction multiply(Fraction f) {
		int num1 = top();
		int num2 = f.top();
		int denom1 = bottom();
		int denom2 = f.bottom();

		int newNum = (num1 * num2);
		int newDenom = (denom1 * denom2);

		return new Fraction(newNum, newDenom);
	}

	public Fraction divide(Fraction f) {
		int num1 = top();
		int num2 = f.top();
		int denom1 = bottom();
		int denom2 = f.bottom();

		int newNum = (num1 * denom2);
		int newDenom = (num2 * denom1);

		return new Fraction(newNum, newDenom);
	}

	public String toString() {
		return top + "/" + bottom;
	}

}

[arithehun]

I'll try it out on the weekend.

[javaAddict]

That is because you never call the reduce. It needs to be put in the constructor so no matter what the user enters your variables will have the right values.

public Fraction(int numerator, int denominator) throws Exception {
	top = numerator;
	bottom = denominator;

	if (bottom == 0);
	    throw new Exception("Attempt to create zero denominator fraction");

        reduce();
	}

With that way in your plus,minus,... methods when you create a new instance and return that object you will have the right values.

Also if you insist on having RuntimeError, change the throws I have at the constructor, but it is advisable to use Exception instead