What's wrong with overridable method calls in constructors?

Question

I have a Wicket page class that sets the page title depending on the result of an abstract method.

public abstract class BasicPage extends WebPage {

    pub         


        

Answer 1

Invoking an overridable method in the constructor allows subclasses to subvert the code, so you can't guarantee that it works anymore. That's why you get a warning.

In your example, what happens if a subclass overrides getTitle() and returns null ?

To "fix" this, you can use a factory method instead of a constructor, it's a common pattern of objects instanciation.