With the protected member m_sessionContext, you find or set the currently active language used by the multi language management:

...
m_sessionContext.setLanguage("de");
...

The value passed to the session context is only valid within the context of current session. Therefore, different users can be logged on to the system choosing different languages.

The string, which is passed to the setLanguage() method of m_sessionContext, represents the name of the directory in which the CSV files are stored. You are not bound to the "de" and "en" directories; you can add any other directories representing additional languages.