Question

I have a Sport base class that has a couple variables. I also have a few different classes derived from Sport such as Volleyball, Soccer, etc. that have additional methods and variables. They look somewhat like this.

public class Sport {
    public String commonVar;
    public Sport(String c) {
        this.commonVar = c;
    }
}

And then Volleyball:

public class Volleyball extends Sport {
    public String onlyVolleyball;
    public Volleyball(String c, String thisVar) {
        super(c);
        this.onlyVolleyball = thisVar;
    }
}

Now I want to be passing the derived classes of Sport into a function elsewhere, but making the parameters

public otherFunction(int one, int two, Sport sport) { }

Only treats sport as a Sport object (it will accept the derived classes but I cannot access any of the variables and methods not common to Sport). My question is how do I create a function that I am able to send all types of Sport derivatives to without losing any data?

Answer 1

You can’t, but you can check if the object is actually a member of the extending class, then cast it and use it, as follows:

public otherFunction(int one, int two, Sport sport)
{
    if(sport instanceof Volleyball)
    {
        Volleyball volley = (Volleyball) sport;
        //Do Volleyball things
    }
    else
    {
        //Only do sport things.
    }
}