Object is null even though I initialized it on creation!

Newbie & Debugging Questions
#1

So, I was making a game state system, and came to this:


Exception in thread "main" java.lang.NullPointerException
	at com.wessles.MERCury.StateCore.addState(StateCore.java:53)
	at com.wessles.horde.Horde.init(Horde.java:46)
	at com.wessles.MERCury.Runner.boot(Runner.java:43)
	at com.wessles.MERCury.Core.<init>(Core.java:39)
	at com.wessles.MERCury.StateCore.<init>(StateCore.java:29)
	at com.wessles.horde.Horde.<init>(Horde.java:34)
	at com.wessles.horde.Horde.main(Horde.java:60)

I looked at the code, and for some reason this is null:


	public void addState(GameState state) {
		gamestates.put(states, state);
		states++;
	}

Even though I initialized gamestate on the class:


	private HashMap<Integer, GameState> gamestates = new HashMap<Integer, GameState>();

So it was initialized, and yet it is null (I checked with (gamestates == null)).
Why?!

EDIT:
I know I could just check for null and then initialize it, but I NEED to know how this could happen.

Also:
Full code