Android file opener for json files only (Java)

Question

I've got a quite simple problem but I can't find the solution...
I would like to have a file picker for my Android app where the user can select only json files.
Following works for all files:

Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.addCategory(Intent.CATEGORY_OPENABLE);
intent.setType("*/*");

startActivityForResult(intent, requestCode);

But how can I restrict it to files with "json" endings?
I tried something like intent.setType("text/*") or intent.setType("text/json") that did not work.
I also tried different things with intent.putExtra(Intent.EXTRA_MIME_TYPES, mimetypes); where mimetypes is a Sring[] that also did not work.

It should actually be quite simple, but I can't find the solution :(