Avoid casting in inherited java-classes

Question

I have a class:

class MyClass {

  public MyClass getParent() { ... }

  public MyClass[] getChildren() { ... }

  ....

}

and a subclass

MySubClass extends MyClass {

  public String getId() { }

  ...
}

Everytime I used getChildren() or getParent() on an instance of MySubClass, I have to cast the result of theese methods, e.g.:

MySubClass sub = new MySubClass();
((MySubClass)sub.getParent()).getId();

Is there any way (by language or design) to avoid that casting?

Thanks for any ideas!

Update What I would like is that getParent() and getChildren() always return the type of the instance they are called from, e.g. sub.getChildren() should return MySubClass[]

Answer 1

Beginning with Java 5.0, you can override methods with covariant return types, i.e. you can override a method to return a subclass parent class. (see Covariant return type in Java):

public class MySubClass extends MyClass {

  @Override
  public MySubClass getParent() {
    return (MySubClass) super.getParent();
  }

  @Override
  public MySubClass[] getChildren() {
    return (MySubClass[]) super.getChildren();
  }

  public String getId() {
    ...
  }
}

You can then call new MySubClass().getChildren()[0].getId().

Of course this will only work if MySubClass always has MySubClass instances as parent and/or children