For spell checking purpose I would like to install an addictional "platform dictionary" in my Eclipse IDE.
You can see the list of platform dictionaries installed in Window > Preferences > General > Editors > Text Editors > Spelling, in the field "Platform dictionary". In my Helios Service Release 1 there are only english of UK or USA. I would to put the language of my country, so I can write comments in my language and have spell check. Eclipse help doesn't explain how.
I am not sure you can add a "Platform dictionary", so that leaves you with a "user defined" one:
Eclipse supports a standard one-word-per-line format for the 'dictionary' file.
You can have several of those at Kevin's Word List on Sourceforge.net, including links to other sites.