You should use in your regex unicode codes for characters, like \u0080.
For German language, I found following table:
Zeichen Unicode
------------------------------
Ä, ä \u00c4, \u00e4
Ö, ö \u00d6, \u00f6
Ü, ü \u00dc, \u00fc
ß \u00df
(source http://javawiki.sowas.com/doku.php?id=java:unicode)