快速浏览一下，您的列表似乎不仅是双向链接的，而且在末端也是相连的(所以它更像是一个 Ring 而不是 like一个列表).换句话说，如果我要遍历您的列表(包含元素 A、B、C、D)，它不会是:

Just from a quick skim, it seems that your list is not only doubly linked, but also is connected at the ends (so it's more like a Ring than like a list). In other words, if I were to iterate over your list (containing elements A, B, C, D), it wouldn't be:

A -> B -> C -> D -> stop

应该是

A -> B -> C -> D -> A -> B -> C -> D -> A -> B ..... etc.

我怀疑这可能是您出现无限循环的原因.

I suspect that could be why you are having an infinite loop.

我会在您的 DoublyLinkedList 类中创建对列表最后一个元素的引用(例如:in.last)，使用它来获取最后一个元素，然后将第一个和最后一个元素链接到 null 或某种 NullListElement extends ListElement

I would create a reference to the last element of your list in your DoublyLinkedList class (example: in.last), use that for getting the last element, and have the first and last elements link to either null or some sort of NullListElement extends ListElement

如果您必须将其保留为环，我仍然会添加对您列表的最后一个元素的引用，以便您可以这样说:

If you must keep it as a ring, I will still add a reference to the last element of your list, so that you can say something like:

if(walker == in.last) break; // stop