CODEWITHSUNDEEP
java
Mariav
Mariav

Reputation: 111

Java Interface in a project involving fractions

I am having trouble in figuring out why the line of code that says Fraction Interface f = etc... does not work. The problem is in .denominator and .numerator. It seems that I am not supposed to implement get methods. So, how I am going to access the denominator and the numerator of aFraction?

Below you also see the methods in the interface. Many thanks.

public class Fraction implements FractionInterface, Comparable<Fraction> {


    private int numerator;  
    private int denominator;    

    public Fraction()
    {

            numerator = 0;
            denominator = 1;
    }   

    public Fraction(int num, int den)
    {

            numerator = num;
            denominator = den;
    }   




    public FractionInterface add(FractionInterface aFraction)
    {
                // return a new Fraction object
                // a/b + c/d is (ad + cb)/(bd)
                // implement this method!

             // WHY .denominator and .numerator do work ?

                FractionInterface f = new Fraction((numerator*aFraction.denominator))
                + (aFraction.numerator * denominator) , (denominator *aFraction.this.denominator));

               return f
        }

}


public interface FractionInterface {
    /** Task: Sets a fraction to a given value.

        public void setFraction(int num, int den);


    public double toDouble();


    public FractionInterface add(FractionInterface aFraction);


    public FractionInterface subtract(FractionInterface aFraction);


    public FractionInterface multiply(FractionInterface aFraction);


    public FractionInterface divide(FractionInterface aFraction);


    public FractionInterface getReciprocal();
}

Upvotes: 0

Views: 975

Answers (2)

Nick Borisenko
Nick Borisenko

Reputation: 494

Try creating a method getNumerator() that calls the numerator variable from this. So when you call this.getNumerator(), it calls the variable numerator associated with the given fraction. This is especially useful when dealing with more than one fraction in a method. Creating a getNumerator() method is as simple as 

public int getNumerator(){
  return numerator;
}

since it just needs to grab the member variables(you don't need to initialize anything). Do the same for the denominator. Now you can call both as foo.getNumerator().

Upvotes: 0

Hovercraft Full Of Eels
Hovercraft Full Of Eels

Reputation: 285403

Give your interface getter method signatures for the numerator and denominator,

public int getNumerator();
public int getDenominator();

implement these in your concrete class, and then call these methods when you need a numerator or denominator.

Upvotes: 1

Related Questions