clear + addAll vs re-initialise list RecyclerViewAdapter android

Question

What's the different between 1 and 2:

1.

public void updatePostList(ArrayList<Post> updatedPosts) {
   this.postList.clear();
   this.postList.addAll(updatedPosts);
   notifyDataSetChanged();
}

2.

public void updatePostList(ArrayList<Post> updatedPosts) {
   this.postList = updatedPosts;
   notifyDataSetChanged();
}

For me, #1 doesn't work as calling this.postList.clear() clears updatedPosts too instead of just clearing postList and I can't understand why.

Seleucia

May be they both refer to same array list, will need to see where both array lists originates – Dandelion

The updatePostList method is inside the CustomRecyclerViewAdapter. The updatedPosts list is sent to this method from the Activity. – Seleucia

The first point represents reusing the same list object. The Second point represents dereferencing and referencing the list from Activity – Fitzsimmons

Yes but the question is why does calling this.postList.clear() clear updatedPosts too instead of just clearing postList. – Seleucia

I think post list is the array list passed to constructor of adapter from activity, may be you are calling updatePostList with the same array list from activity, csn u pls share your activity code? – Dandelion