Question

This code is not mine and i need to add some improvements to it, but i’m stuck in this problem.

I have an abstract class “CallNode” and a lot of subclasses, one of them is “Call”. The “Checker” class is intercepting missed calls, but return them as CallNode. My problem is that i need to get the id of this call, but i can’t access it by CallNode.

Do you have any suggestions to solve this problem?

I let you the code, so that you can better understand the problem:

public abstract class CallNode {
    public abstract CallNode hasMissingCall();
}

public class Call extends CallNode {
    public int id;

    // Simplification of method
    public CallNode hasMissingCall() {  
        if (true)
            return this;
        // ...
    }
}

public class Checker{
    private static CallNode rootExpected;

    CallNode missing = rootExpected.hasMissingCall();

    System.out.println( missing.id ); // THE PROBLEM!!!
}

Thank’s in advance!!!

Answer 1

Define a template method returning the id in the abstract class:

public abstract class CallNode {
    public abstract CallNode hasMissingCall();

    public abstract int getId();
}

let subclass implement it:

public class Call extends CallNode {
    public int id;

    // Simplification of method
    public CallNode hasMissingCall() {  
        if (true)
            return this;
        // ...
    }
    public int getId()
    {
         return this.id;
    }
}

That’s an option. Personally I’ll move the id field upward in the CallNode class, since I think it’s supposed to be unique and shared by all subclasses.