The following paths worked for me:

deb ftp://ftp.gwdg.de/pub/languages/java/linux/debian sarge non-free
deb-src ftp://ftp.gwdg.de/pub/languages/java/linux/debian sarge non-free
deb ftp://ftp.gwdg.de/pub/languages/java/linux/debian/ unstable non-free
deb-src ftp://ftp.gwdg.de/pub/languages/java/linux/debian/ unstable non-free

The name of the distribution (sarge, unstable, etc.) automatically includes the "dist" directory. The "binary-i386" or "sources" directory is also automatically appended, so you shouldn't include it in sources.list.