Also looking for a way to change the jre's default font, editing fontconfig.properties
worked for me actually (oracle java 6, linux in my case):
edit
jre/lib/fontconfig.Ubuntu.properties
To change the default font replace all
DejaVu Sans
withUbuntu
for example, and add the path to the font files:# Font File Names filename.Ubuntu=/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-R.ttf filename.Ubuntu_Bold=/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-B.ttf filename.Ubuntu_Oblique=/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-RI.ttf filename.Ubuntu_Bold_Oblique=/usr/share/fonts/truetype/ubuntu-font-family/Ubuntu-BI.ttf filename.Ubuntu_Mono=/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-R.ttf filename.Ubuntu_Mono_Bold=/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-B.ttf filename.Ubuntu_Mono_Oblique=/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-RI.ttf filename.Ubuntu_Mono_Bold_Oblique=/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-BI.ttf