Is jdk provided doubly linked list circular?

Question

Is java doubly linked list circular ?

It nowhere written in java docs. But looks likes its circular when i see linked list source code Here is the relevant code snippet if

private Entry<E> More ...entry(int index) {
...
        Entry<E> e = header;
        if (index < (size >> 1)) {
           ...
        } else {
             for (int i = size; i > index; i--)
                e = e.previous;
        }
        return e;
    }

Update :- By circular i mean

1. header previous node should be last node which seems true here
2. And for last node next node should be header node

Answer 1

Going by your criteria

1. header previous node should be last node which seems true here
2. And for last node next node should be header node

Linked list is circular because if you see add method implementation which internally calls addBefore , entry you going to insert points to header as next link and header points to last entry you just inserted as previous link

Answer 2

It's not circular. It has a clear Head and Tail.