Non-ASCII characters are displayed as question marks

OS: Linux
Problem description: Filenames and/or extracted folders/files contain question marks instead of the expected names.
Solution:
Either fix your OS' locale setting or add the following lines to your JDownloader start script prior to the JD start:

export LC_CTYPE="en_US.UTF-8"
export LANG="en_US.UTF-8"
export LC_COLLATE="C"