Java 8 parallelism / concurrency. Reading and writing to output files.

I have some code that will open a mass spectrometry raw file, read the information, and output the data for each scan into an output xml file. Right now I have this done sequentially and in a thread safe manner but I would like to run this in parallel and when I try to do this it crashes. The jobs can be separated completely 100% meaning if I have rawfile1 writing to directory1, and rawfile2 writing to directory2. There is no need for the code to be reading or writing to the same file at the same time.

Sending the code may be difficult but I can do this if needed. All that may be needed is to have a skype or google meet session in which I can share my screen and show the code and you can maybe write a template for my code that will solve this issue using Java concurrent methods. I want to either have the users input how many CPUs they want manually, or the code can see how many CPUs are available. Based on this instead of running one

If this works out I also have at least two other parallel Java jobs.