private void unlink(final Entry<K, V> e) {
    final Entry<K, V> prev = e.previous;
    final Entry<K, V> next = e.next;
    if (prev != null) {
      prev.next = next;
    }
    else {
      top = next;
    }
    if (next != null) {
      next.previous = prev;
    }
    else {
      back = prev;
    }

    // Help GC
    e.previous = null;
    e.next = null;
  }
private void unlink(final Entry<K, V> e)