java.util.MissingResourceException: Can't find bundle for base name 'property_file name', locale en_US

Try with the fully qualified name for the resource:

private static final String FILENAME = "resources/skyscrapper";

ResourceBundle doesn't load files? You need to get the files into a resource first. How about just loading into a FileInputStream then a PropertyResourceBundle

   FileInputStream fis = new FileInputStream("skyscrapper.properties");
   resourceBundle = new PropertyResourceBundle(fis);

Or if you need the locale specific code, something like this should work

File file = new File("skyscrapper.properties");
URL[] urls = {file.toURI().toURL()};
ClassLoader loader = new URLClassLoader(urls);
ResourceBundle rb = ResourceBundle.getBundle("skyscrapper", Locale.getDefault(), loader);

Use the Resource like

ResourceBundle rb = ResourceBundle.getBundle("com//sudeep//internationalization//MyApp",locale);
or
ResourceBundle rb = ResourceBundle.getBundle("com.sudeep.internationalization.MyApp",locale);

Just give the qualified path .. Its working for me!!!