How to associate an instance variable if all the code is inside a run() method?

Question

I'm supposed to be creating a game, and we've been given free rein in creating it...but I have no idea what I'm doing. I copied the format of a previous lab, because I needed a way to run it, but now I have a problem. My Gui class is as follows:

public class Gui implements Runnable {
    public Gui() { }
    ArrayList<Tile> _al;

    @Override
    public void run() {
          //where I want the _al variable to be used
    }
}

The code I copied used a Driver class to run this method:

public class Driver {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Gui());
    }
}

We haven't discussed this method in class, but from Googling I understand that this is necessary for the program to work. There's been a massive jump in the difficulty of the labs, so I am now lost. I'm sure there's a simple way to format all the code, but I have no idea what the relationship is between the run method and the main, or how I can make it so an association relationship can be made in my code. Nothing I've searched really helped, so I hope this question's okay.

How to associate an instance variable if all the code is inside a run() method?

Answer 1

You've done it right. You can use _a1 in the run method.

_a1 is an instance variable. You can tell this because it does not have the static modifier. Likewise, run is an instance method. Therefore it has access to _a1. Each new instance of Gui gets its own instance of _a1 however.

If that's not what you want, the absolute simplest fix is to add the static modifier to _a1. Then it will be shared across all instances of Gui and can still be accessed from run. I believe Swing does not run runnables concurrently so there shouldn't be concerns with parallel access.