Java generics to enforce return type of abstract method

Question

I have the following situation :

abstract class X { abstract X someMethod (...) {...} }.

Now I want to constrain any implementation of X to

Answer 1

Here's an approach that lets you return a parameter type for this:

AbstractFoo> {
  /** Subclasses must implement to return {@code this}. */
  protected abstract T getThis();

  /**  Does something interesting and returns this Foo */
  public T inheritedThing {
    /* blah di blah */
    return getThis();
  }
}