to Felix Knecht,
.xml file can be modified by non-programmer end users. While .properties file can only be modified by Java programmers.
It seems eclipse plug-in only support multi-language with .properties files.
I have finished some projects with multi-language based on .xml files. And the translation task is been done by a professional translation company. I think this is a good working-model.
Generally, multi-language task can be implement in following ways:
a. plain text files, such as .xml files, .ini files,
b. encoding text files, such as .properties files.
c. binary files. such as mysql errmsg.sys
d. database tables.
If we use plain text files, end user will easily add new language based on English language files with a text editor.
And database tables make it easy to query if there is any missing, for example, from 1.0 to 1.1, english langauge add 50 items, while chinese add 44 items. SQLdatabase make it easy to find out.
for .properties, I don't think there is any advantages for multi-langauge.