You have a
lot of typos. Remember that Java is case-sensitive, so System is not the same as system. As well as altering your file's name, you will need to: correct the spelling for JButon, mkMeni and setVisable; capitalize the first letter of all classes, including String, System, and Font; properly capitalize JMenu
bar and Resource
bundle; and at some point declare and initialize the variable I18N before using it.
EDIT: Random Spirit beat me to the punch... although the most serious error in your code, as I pointed out, is the uninitialized I18N variable (or class?). It appears your code is attempting to utilize internationalization functionality; see
this tutorial for help.