Regarding the implementation issues of java collection LinkedList

Question

public E removeLast() {
    final Node<E> l = last;
    if (l == null)
        throw new NoSuchElementException();
    return unlinkLast(l);
}

last is a member variable. Why not use it directly in the method, but assign it to a final local variable?

Answer 1

Looked at the code

    transient Node<E> last;

last is transient, right? If you assign it to a local final variable, you don’t need to check the value every time you use last, right?

Answer 2

Part of the reason is to ensure thread safety. Assuming that this method does not use the l variable but directly references the last member, then the judgment becomes if(this.last == null). If last is assigned to null immediately after passing the judgment, then the next sentence unlinkLast(this.last) will have an unknown result.