Recursive method for outputting files while maintaining hierarchy

Question

You need to implement a recursive method that will list all folders within a folder, thus:

mainDir |--dir1 | |--dir11 | |--dir12 | |--dir121 |--dir2 | |--dir23 | |--dir231 |--dir3

As an argument, you can take only the path to the folder itself, and I just won’t understand how to indent the names.

To get an answer, explain what exactly you see the problem, how to reproduce it, what you want to get as a result, etc. Give an example that clearly demonstrates the problem.
Good afternoon, the problem is described just above, I do not understand how to display the hierarchy, if I may say so.
That is, in front of a file that is 2 levels deeper there were 4 spaces, and before that it is 3 - 6.
In the recursive method, pass the value of the indent (the number of spaces).
For the original ( mainDir ) - 0. And judging by the general logic, with zero indent |
The only thing I can pass to the method is the path to the file, and nothing else.
I apologize if it was not clearly expressed when I wrote this about it.
You can not forward the indent as a parameter to a method, but store the current indent as, for example, a static field, but the method parameter is the preferred option.

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