Removed Type-Defect label.
Added Type-Enhancement, Area-Library, Triaged labels.

Splay trees are not really built for iteration. If you even read from the tree while iterating, it changes its structure. However, it isn't suitable to throw a ConcurrentModificationError due to a reading operation, so we'll have to handle it behind the scenes (somewhat inefficiently).

Iteration would be easier if we added a parent link, but that would be an overhead when it's not used.

It would probably be better to have a stable tree structure (AVL or Red/Black trees) as well. They have a slightly higher overhead, but better guarantees/worst case behavior. For those, an "iterateFrom/bidi-iterator" would make more sense.

Ah, I didn't notice the missing parent link. I can just pull over an AVL implementation from java.