I think it's unnecessary clutter.  The contract with the `Context` is that, if it has a `destroy` method, the `Context` will call it.  The `Context` doesn't need, nor will it call, an `isDestroyed` method.  If your class that is adding something to the cache wasn't to query whether the object is destroyed, or if you're planning to share that object with the wider world, then adding an `isDestroyed` is a good idea.  Otherwise, save yourself some typing and leave it out.