Accessing static field avoided by referencing Class?

Question

I'm not understanding why this is working, please help educate me.

Config CFIG = new Config();
Tile selectedTile = CFIG.tileGallery.get(1);
System.out.println("This is the name:" + selectedTile.getName());
Feature selectedFeature = CFIG.featureGallery.get(3);
System.out.println("This is the name:" + selectedFeature.getName()+ 
    " " + selectedFeature.getEffect(0));

I initialize the object CFIG, which sets both the member variables of the Class Config tileGallery ArrayList and featureGallery ArrayList. When I run the code, it works, outputting the selected test values. However for both of the declarative statements Netbeans gives a warning of "Accessing static field "

Using the hint of "Replace with class reference", it changes the statements to:

Tile selectedTile = Config.tileGallery.get(1);
Feature selectedFeature = Config.featureGallery.get(3);

When I run it, it still works!

Question, Config. isn't identifying which Config object to call data from. Now I only have a single Config Object in existence, but even if I initialize a second Config object it still doesn't appear confused.

What's going on here?

EDIT: andih wondered what the code of the Config Class. I didn't add it, because it wasn't much, and figured you could easily assume what it did as it pertains to the issue. However, here it is, just in case.

public class Config {
    public static ArrayList<Tile> tileGallery;
    public static ArrayList<Feature> featureGallery;

    public Config (){
        this.tileGallery = Tile.ReadTileXML();
        this.featureGallery = Feature.ReadFeatureXML();
    }
}

A static variable is shared between all instances of that class. If `tileGallery` should be bound to a specific instance of the `Config` class make the `static` access specifier. — SubOptimal, Jul 05 '16 at 03:44
Bonus question, after changing all of the statements to use Config rather than CFIG, a new "warning" is displayed that just says "Introduce..." Alt+Enter doesn't offer any additional information. Again, thanks to those who offered answers, I learned something from this. — JamesA, Jul 05 '16 at 04:20

score 3 · Answer 1 · answered Jul 05 '16 at 03:57

The static keyword means this field belongs to the class than instance of the class. Even if you create hundred objects , this field will be shared amoung them. These static fields "tileGallery" and "featureGallery" from each instance will be pointing to same object in memory.

The static variable gets memory only once in class area at the time of class loading.

score 1 · Accepted Answer · answered Jul 05 '16 at 03:58

Without the exact code of your Config class it's hard to say but it looks like your Config class uses static fields like

   public class Config {
      public Config() { 
         titleGallery = new ArrayList();
         titleTallery.add(new Title());
      }

      public static List<Title> titleGalery;
    }

That's what the hint says.

In this case all your Config instances share the same titleGalery and you can access them via Config.titleGalery.

If you want different Configinstances with different value you'll have to remove the static keyword to get independent instance fields.

public class Config {
      public Config() { 
         titleGallery = new ArrayList();
         titleGallery.add(new Title());
      }

      // old: public static List<Title> titleGalery;
      public List<Title> titleGalery;
    }

Doh! I thought it meant something different. =) – JamesA Jul 05 '16 at 04:08 — JamesA, Jul 05 '16 at 04:08

Accessing static field avoided by referencing Class?

2 Answers2