如何在Java中使用递归算法来保持“完成的事情”？

I have a recursive algorithm which steps through a string, character by character, and parses it to create a tree-like structure. I want to be able to keep track of the character index the parser is currently at (for error messages as much as anything else) but am not keen on implementing something like a tuple to handle multiple returned types.I have a recursive algorithm which steps throug