record chunks and tell when player is in them

Hey, I am trying to find a way to record certain chunk coordinates and I am not to sure on how to go about doing that and then tell when the player is in those chunks.

My first thought would be a hashmap so something like

Code:

public static HashMap<Chunk, ChunkInfo> chunks = new HashMap<Chunk, ChunkInfo>();

ChunkInfo will be a class I make so I can assign each chunk certain properties.

Now I am not to sure how to tell when a player is in those chunks. I could loop through the hashmap but that would cause some lag.

Any ideas?