Question

I am trying to get an array to take a variable number of objects as input. I am new to programming so I apologize in advance.

Here is my code:

public class Rating{
    double [] Ratings;
    int CustomerID;
    int Domain;

    public Rating (int id, int d, double [] x) {
        double [] Ratings = x;
        int CustomerID=id;
        int Domain=d;
    }
}

public class All_user{
    double [] All_users;

    public All_user(Rating...argument) {
        double [] All_users={Rating...argument};
    }
}

However, I am get this error associated with double[] All_users={Rating..arguments);:

    Multiple markers at this line
 - Syntax error on token "...", . expected
 - arguments cannot be resolved or is 
  not a field

Any thoughts? Thanks in advance!

Answer 1

The problem comes in your All_user class constructor; you’re trying to set… something… of type Ratings[] to a class member of type double[]

You could do one of the following :

1- Have your All_user‘s constructor receive an array (or variable-length arguments) be instances of Rating and simply assign it to the class member (an array) of the same type :

public class All_user{
    Rating [] All_users;

    public All_user(Rating...argument) {
        All_users = argument;  // arguments is a Rating[]
    }
}

or collect all values (double Ratings) from each Rating and map them into an array

public class All_user{
    double [] All_users;

    public All_user(Rating...argument) {
        ArrayList<Double> ratings = new ArrayList<Double>();
        for (Rating r : argument) {
            for (double d : r.Ratings) ratings.add(d);
        }
        All_users = new double[ratings.size()];
        for (int i=0; i<ratings.size(); i++) All_users[i] = ratings.get(i);
    }
}

I think the latter is what you are trying to do. Also, note that your Rating class could also be rewritten as

public class Rating{
    double [] Ratings;
    int CustomerID;
    int Domain;

    public Rating (int id, int d, double...x) {
        double [] Ratings = x;
        int CustomerID=id;
        int Domain=d;
    }
}

FYI: The variable-length argument is always the last one in the declared arguments. More on varargs here and here.