Please refer to attached screenshot images.
compare_encoding.eog show the same sample program started without -Dfile.encoding=UTF-8 (left) and with the option added by NB(right).
compare_laf.png show the same program in system laf (left) and nimbus laf (right), both with -Dfile.encoding=UTF-8.

This seems to happens when
- User is running Japanese Windows
- Look and Feel is Nimbus
- used -Dfile.encoding=UTF-8

This -Dfile.encoding=UTF-8 is a common case when Japanese developer sets file encoding to utf-8 (different from platform windows-31j) in NetBeans or Eclipse and started the program through IDE. When they run their application by itself, there will be no problem as no IDE adding file.encoding=UTF-8 but they ofcourse want to start programs from IDE while development.

I am reporting this to classes_fontprop as following change in fontconfig.properties worked as a work around. But in case the fix should be in swing or other components, please transfer to appropriate team.

#sequence.allfonts.UTF-8.ja=alphabetic,japanese,devanagari,dingbats,symbol
sequence.allfonts.UTF-8.ja=alphabetic,japanese,dingbats,symbol