Maximum number of folders in one folder (ext4)?

Question

Java

Maximum number of folders in one folder (ext4)?

Answer 1

I will assume that the key line in the trace is
The application cannot be launched more than once.
But in general .. what you want to do, I did not understand the code.

Answer 2

Maximum number of folders in one folder (ext4)?

There is no limit.
There is a limit on the total number of files in one file system - 2^32, they can all be dumped into one directory.