Implementations and Collections

Question

Why does this not work...

public ArrayList getEdges() {

return A;

//A is an Arraylist of type \'Action\'. Action implements Ed         


        

Answer 1

Because while Edge is a subtype of Action, ArrayList is not a subtype of ArrayList.

Use ArrayList instead.

You could take a look at this tutorial's 4. Wildcard section, although I'd suggest to just read through it, because it is really helpful.