Write variable from other function

[Suliman]

> When you declare variable static it makes it shared between all 
> instances of that class, allowing to use it without any 
> specific instance. When you declare method as static you say to 
> compiler that it is not going to use any non-static fields of 
> the class (normally available via "this" pointer) and make it 
> possible to call it as `Config.method`.

Thanks! I know about static, but now I need experience to work 
with class constructor. So now I can't understand what I can do 
with error: "Error: need 'this' for 'isConfigExist' of type 
'bool()'"