I don't get the findAll and then append thing.

What he means is, we are not going to return the list itself which he have as a member variable in the class. We aren't doing that because in that case, the caller of the method will get the list, and can do whatever he wants with it and those changes will be reflected in our member variable. So we don't want that, which is why we are making an exact copy of the list we have and hand that over as a return value, so if additional changes are done to that particular list we returned, they won't be reflected in our "original" list so to speak.

An analogy would be, you ask for a list of teacher names at a university and the local admin hands you a list on paper. Now, imagine if whenever you add a name to that paper, or strike out a name, the original list the admin has is also updated with the changes you make at home, which isn't good. Instead, the admin should give you a list on paper which doesn't have this "connection" to the original list, so whatever you do to the list, isn't reflected in the original.

It's all because in Java what we are returning is a reference to the object and the reference we return shouldn't point to our original member variable object. So in order to not keep this "connection" alive, we are creating a new object with the exact same contents as the original one and hand a reference to that copied object over and don't worry what happens with it.

Hope it makes more sense now :).