Referencing non static variable from within static Inner Class

Question

I need to reference a variable of a top level class from a method within a static class.

This method should act on unique instances of the top level class and so it feels like I shouldn't instantiate the top level class inside the static class.

Basically I want something like

public class TopLevel{ // private int innerV public static class Inner implements X { for(i=0; i<innerV,i++){ doSomething } } }

Is it possible to just say this.innerV or something similar in the for loop and similar places?

Please review my edit - I have corrected the code formatting. Ty. — lzap
– lzap, Commented May 25, 2011 at 8:16

Péter Török · Accepted Answer · 2011-05-25 08:17:51Z

From a static inner class, you can't refer to (nonstatic) members of the outer class directly. If you remove the static qualifier, it will work, because instances of nonstatic inner classes are implicitly tied to an instance of the containing class, so they can refer to its members directly.

Declaring your inner class static removes this link, so you need to either pass an instance of the outer class to the inner class method (or its constructor) as a parameter, or create it inside the method.

I was hoping there was a way around this. There are some problems with removing "static" for my specific application....will try to figure it out. Thanks for letting me know there's no cheat solution though!

lzap · Accepted Answer · 2011-05-25 08:10:06Z

You can't do that. Create a TopLevel instance and if you make an innerV accessor (getter/setter) or make it public, than you can.

public class TopLevel { public int innerV public static class Inner implements X { for(i=0; i<innerV,i++){ TopLevel tl = new TopLevel() tl.innerV = 12345678; } } }

Just as an aside: don't you need to assign t1.innerV before the for loop?
Yes something like that. Java defaults to zero for ints so it compiles but the loop never gets executed btw.

user207421 · Accepted Answer · 2011-05-26 00:24:27Z

You can't do that because it doesn't make sense, any more than referring to a non-static member from a static function makes sense. There is no current instance of the outer class in the context of the static inner class to get the instance variable from.

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