Swing/AWT/SWT :: How To Share Member Variables

I can understand basic concepts such as OOP, Threads, Events and GUI, I've coded a little but I've always had this bothering me:

Explaining by example:

public class X{
int x;
String y;
public static void main(String[] args){
x = 10;
y = "hello ";

[Code] ....

Okay, i'm pretty certain that code won't work, but I just want to show you conceptually, not actually care whether the code works or not. In case I wanted to get that code to work I should have probably used a Swing application to get a KeyListener in the first place, but I guess I know that, and if this was working, what would happen theoretically is, the code would run, initialize x to 10, and y to hello, then when a key is pressed, it will update x to 11 and y to hello world, I'm pretty sure that's what happens.

In this case, I used a inner class to update it's parent's members, I've seen this done before and I can vouch for the fact that it's a legitimate way to code a class.

Now in this example:

class X{
int x;
String y;
public int getX(){ return x; }
public String getY(){ return y; }

[Code] ....

So in this overly complicated example, i'm trying to share class X with both class Y and class Z, just that how to share the members of class X with the different classes without making a new instance of X. In the previous example, I could access the parent's members because the inner class was implicitly capable of accessing the parent's members. However in this case, If "Y" starts an instance of X, then how do I access it? because it's a side by side class not a hierarchy for me to access the parent's members.