protected T popFrontEntry() {
        if (head == null) {
            return null;
        }
        T next = head.getNext();
        if (next != null) {
            next.setPrev(null);
        } else {
            last = null;
        }
        T e = head;
        head = next;
        e.setNext(null);
        size--;
        return e;
    }
protected T popFrontEntry ( ) { if ( head == null ) { return null ; } T next = head . getNext ( ) ; if ( next != null ) { next . setPrev ( null ) ; } else { last = null ; } T e = head ; head = next ; e . setNext ( null ) ; size -- ; return e ; }
Removes and returns the first entry in the list. If the list is empty, it remains unmodified and
<code>null</code> is returned.

@return the previously first entry in the list, or <code>null</code>.