Install the patch providing Euro currency support on Solaris 2.6 - see:
/net/sunsoftpatch/patches/temporary/T106842-01
If you don't have them yet, this also requires the following patches:
/net/sunsoftpatch/patches/temporary/T106841-01
/net/sunsoftpatch.eng/patches/patchdb/unbundled/openwin/3.6/105633-11

Reboot your machine, choose the de.ISO8859-15 locale from the login screen.

Copy the source of the application /java/jdk/1.1.7/ws/MASTER/java/text/resources/EuroGUI to a private location, compile it. Run it using the command line option -Dfile.encoding=ISO8859_15_FDIS to work around bug 4171977.

In the text fields, you should see the text "Euro:<EURO>". Instead, you see the text "Euro:<NOT SIGN>". This text is entered into the text fields using setText().