java - Circularly linked list remove tail without loop -

i tried implement circularly linked list , had read complexity of removing tail (which has direct reference) o(1). can't rid of tail reference without looping , resulting in complexity of o(n) , wondering if @ possible without looping?

    remove =   tail;     prev        =   temp    =   tail.getnext();          {         prev    =   temp;         temp    =   temp.getnext();     }     while(!temp.getnext().equals(tail.getnext()));      prev.setnext(temp.getnext());     size--;     return remove; 

note: prev, temp, removeare local , tail tail of list , first instance of tail.getnext() head.

i had tried below not work node before tail still points tail , reference isn't removed. know need make tail's previous point head in order remove tail , above code this, i'm unsure how , if it's possible without looping through list..

    remove =   tail;     tail=   lastnode.getnext();     size--;     return remove; 

in circularly linked list every node has previous , next. there head pointer first node, , previous tail node, next head node.

so

node removetail() {      if (head == null) {          return null;      }       node tail = head.previous;      node newtail = tail.previous;      newtail.next = head;      head.previous = newtail;       if (head == tail) {          head = null;      }      --size;      return tail; // if desired. }