clear + addAll vs re-initialise list RecyclerViewAdapter android

问题

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.

来源：https://stackoverflow.com/questions/56454443/clear-addall-vs-re-initialise-list-recyclerviewadapter-android