Java ADT calling variables

Question

I'm new to Java and I'm trying to create an ADT. My ADT involves creating and processing fractions through input of a numerator and denominator. I want one of my methods to add two fractions together and return a simplified fraction based on the gcd of the two sums. The problem I'm having is with instantiating the components of the two fractions(the numerator and denominator). The method should take a fraction other, denoted public Rational add(Rational other). The first variables I assigned were

int d1 = this.denominator;
int d2 = other.denominator;

but this doesn't seem to work. Below is the method thus far:

public Rational add(Rational other){
  int d1 = this.denominator;
  int d2 = other.denominator;
  int dtotal = d1*d2;
  int n1 = this.numerator*d2;
  int n2 = other.numerator*d1;
  int ntotal = n1+n2;
  if(ntotal>dtotal){
    for(int i=1; i<=ntotal; i++){
      if(ntotal%i==0 && dtotal%i==0){
        gcd=i;
      }
    }
  }else if(dtotal>ntotal){
    for(int i=1;i<=dtotal;i++){
      if(dtotal%i==0 && ntotal%i==0){
        gcd=i;
      }
    }
  }else if(dtotal==ntotal){
    gcd=numerator;
  }
  numerator = ntotal/gcd;
  denominator = dtotal/gcd;
}

Answer 1

You need to define your interface outside of the class with the required methods. Here is the sample, please edit as per your needs.

interface Rational {    
  public int getNumerator();
  public int getDenominator();
  public Rational add(Rational other);
  public Rational multiply(Rational other);
  public int compareTo(Rational other);
}

Now your class should be defined like this:

public class RationalC implements Rational {

  int gcd;
  int numerator;
  int denominator;


  @Override
  public int getNumerator() {
    return numerator;
  }

  @Override
  public int getDenominator() {
    return denominator;
  }

  @Override
  public Rational add(Rational other) {
    return null;
  }

  @Override
  public Rational multiply(Rational other) {
    return null;
  }

  @Override
  public int compareTo(Rational other) {
    return 0;
  }
}

Add your add, multiply method definition. Use the getNumerator() and getDenominator() to access the values instead of directly accessing them.