If you're having trouble with using Japanese fonts in Java when running Debian unstable, here's what I did to get them working:

First, make sure that you have "Xfs-xtt" installed and running.

Then, make sure that in your XF86Config-4 you have the Xfs-xtt port included:

Section "Files"
        FontPath        "unix/:7110"                    # Xfs-xtt
        FontPath        "unix/:7100"                    # The bog standard Xfs

Then, install the japanese fonts:

   apt-get install ttf-xtt-watanabe-mincho

Then take the following file and use it to replace your "jre/lib/font.properties" -file:

#
# Serif font definition
#
serif.0=-b&h-lucidabright-medium-r-normal--*-%d-*-*-p-*-iso8859-1
serif.1=-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

serif.italic.0=-b&h-lucidabright-medium-i-normal--*-%d-*-*-p-*-iso8859-1
serif.italic.1=-watanabe-mincho-medium-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

serif.bold.0=-b&h-lucidabright-demibold-r-normal--*-%d-*-*-p-*-iso8859-1
serif.bold.1=-watanabe-mincho-bold-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

serif.bolditalic.0=-b&h-lucidabright-demibold-i-normal--*-%d-*-*-p-*-iso8859-1
serif.bolditalic.1=-watanabe-mincho-bold-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

# SansSerif font definition
#
sansserif.0=-b&h-lucidasans-medium-r-normal-sans-*-%d-*-*-p-*-iso8859-1
sansserif.1=-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

sansserif.italic.0=-b&h-lucidasans-medium-i-normal-sans-*-%d-*-*-p-*-iso8859-1
sansserif.italic.1=-watanabe-mincho-medium-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

sansserif.bold.0=-b&h-lucidasans-bold-r-normal-sans-*-%d-*-*-p-*-iso8859-1
sansserif.bold.1=-watanabe-mincho-bold-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

sansserif.bolditalic.0=-b&h-lucidasans-bold-i-normal-sans-*-%d-*-*-p-*-iso8859-1
sansserif.bolditalic.1=-watanabe-mincho-bold-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

# Monospaced font definition
#
monospaced.0=-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1
monospaced.1=-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

monospaced.italic.0=-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1
monospaced.italic.1=-watanabe-mincho-medium-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

monospaced.bold.0=-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1
monospaced.bold.1=-watanabe-mincho-bold-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

monospaced.bolditalic.0=-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1
monospaced.bolditalic.1=-watanabe-mincho-bold-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

# Dialog font definition
#
dialog.0=-b&h-lucidasans-medium-r-normal-sans-*-%d-*-*-p-*-iso8859-1
dialog.1=-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialog.italic.0=-b&h-lucidasans-medium-i-normal-sans-*-%d-*-*-p-*-iso8859-1
dialog.italic.1=-watanabe-mincho-medium-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialog.bold.0=-b&h-lucidasans-bold-r-normal-sans-*-%d-*-*-p-*-iso8859-1
dialog.bold.1=-watanabe-mincho-bold-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialog.bolditalic.0=-b&h-lucidasans-bold-i-normal-sans-*-%d-*-*-p-*-iso8859-1
dialog.bolditalic.1=-watanabe-mincho-bold-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

# DialogInput font definition
#
dialoginput.0=-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1
dialoginput.1=-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialoginput.italic.0=-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1
dialoginput.italic.1=-watanabe-mincho-medium-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialoginput.bold.0=-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1
dialoginput.bold.1=-watanabe-mincho-bold-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

dialoginput.bolditalic.0=-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1
dialoginput.bolditalic.1=-watanabe-mincho-bold-i-normal--*-%d-*-*-p-*-jisx0208.1983-0

# Default font definition
#
default.char=274f

# name aliases
#
alias.timesroman=serif
alias.helvetica=sansserif
alias.courier=monospaced

# for backward compatibility
#zapfdingbats.0=-urw-itc zapfdingbats-medium-r-normal--*-%d-*-*-p-*-sun-fontspecific

# Static FontCharset info.
#
# This information is used by the font which is not indexed by Unicode.
# Such fonts can use their own subclass of FontCharset.
#
# This information can be overriden by describing more specific style.
# For example
#
#  fontcharset.serif.plain.3=SpecialSymbols
#  means serif.plain.3 font's index can be retrieved with the convert() method
#  of instance of SpecialSymbols and what kind of characters serif.plain.3 font
#  has can be judged with the isCovered() method of instance of SpecialSymbols.
#
fontcharset.serif.0=sun.io.CharToByteISO8859_1
fontcharset.serif.1=sun.awt.motif.CharToByteX11JIS0208

fontcharset.sansserif.0=sun.io.CharToByteISO8859_1
fontcharset.sansserif.1=sun.awt.motif.CharToByteX11JIS0208

fontcharset.monospaced.0=sun.io.CharToByteISO8859_1
fontcharset.monospaced.1=sun.awt.motif.CharToByteX11JIS0208

fontcharset.dialog.0=sun.io.CharToByteISO8859_1
fontcharset.dialog.1=sun.awt.motif.CharToByteX11JIS0208

fontcharset.dialoginput.0=sun.io.CharToByteISO8859_1
fontcharset.dialoginput.1=sun.awt.motif.CharToByteX11JIS0208

# exclusion info.
#
# This information describe exclusion ranges for each fonts.
#
# 'exclusion.serif.plain.0' overrides 'exclusion.serif.0', and
# 'exclusion.serif.0' overrides exclusion.0, and so on.
#

# XFontSet string
# X11 only properties
#

# Serif font definition
#
fontset.serif.plain=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidabright-medium-r-normal--*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.serif.italic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidabright-medium-i-normal--*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.serif.bold=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidabright-demibold-r-normal--*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.serif.bolditalic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidabright-demibold-i-normal--*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

# SansSerif font definition
#

fontset.sansserif.plain=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-medium-i-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.sansserif.italic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-medium-i-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.sansserif.bold=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-bold-r-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.sansserif.bolditalic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-bold-i-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

# Monospaced font definition
#
fontset.monospaced.plain=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.monospaced.italic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.monospaced.bold=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.monospaced.bolditalic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

# Dialog font definition
#
fontset.dialog.italic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-medium-i-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialog.bold=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-bold-r-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialog.bolditalic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-bold-i-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialog.plain=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-medium-r-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

# DialogInput font definition
#
fontset.dialoginput.italic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialoginput.bold=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialoginput.bolditalic=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-bold-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

fontset.dialoginput.plain=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucidatypewriter-medium-r-normal-sans-*-%d-*-*-m-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0

#
fontset.default=\
-sony-fixed-medium-r-normal--*-%d-*-*-c-*-jisx0201.1976-0,\
-b&h-lucida-medium-r-normal-sans-*-%d-*-*-p-*-iso8859-1,\
-watanabe-mincho-medium-r-normal--*-%d-*-*-p-*-jisx0208.1983-0
#

You'll then probably need to restart your X and fontserver as well. Good luck!