Creating a User Defined Language in Notepad++

In notepad++ you can bring up the User Defined Language editor from the menu (View & User Define Dialog...):

There are four tabs to fill out - Folder (as in code folding), Keyword, Comment, and Operators. (For a more in depth overview of the User Defined Language system, check out the Notepad++ docs) Make sure to set the file extension and language name. There's no save button, which is a little confusing, but the changes take effect as you make them.

Installing a user defined language file that someone else has written is pretty simple: In window click import and select user defined language xml file and this will appear in User Language list box.

I have created xml file for support FTL (download from here)

If you want see your custom language file as exist language then open Setting & Style Configure  and select which language (for example "Java"). Bottom u'll see supported extension for that language (for example "java"), and write your extension in "User ext." field, press "Save & Close"

If you want auto-completion then go Settings & Preferences select "Backup/Auto-completion" tab and check "Enable auto-completion on each input" and restart notepad++ :)

Thanks ...