Slick2D中的Unknown NullPointerException

Question

I am trying to understand the basics of making a game in Slick2D. I have 4 classes: Main , Entity , Misc (pastebin.com/e5WqF6Ma) and Fish (pastebin.com/ie0ANxxx)

Whenever I run the code, this is the console log.

Mon Aug 17 00:15:07 BST 2015 INFO:Slick Build #237
Mon Aug 17 00:15:07 BST 2015 INFO:LWJGL Version: 2.9.3
Mon Aug 17 00:15:07 BST 2015 INFO:OriginalDisplayMode: 1366 x 768 x 32 @60Hz
Mon Aug 17 00:15:07 BST 2015 INFO:TargetDisplayMode: 640 x 480 x 0 @0Hz
Mon Aug 17 00:15:08 BST 2015 INFO:Starting display 640x480
Mon Aug 17 00:15:08 BST 2015 INFO:Use Java PNG Loader = true
Mon Aug 17 00:15:08 BST 2015 INFO:Controllers not available
Exception in thread "main" java.lang.NullPointerException
    at com..prototypes.project_blueberry.util.Misc.addID(Misc.java:24)
    at com..prototypes.project_blueberry.util.Entity.<init>(Entity.java:16)
    at com..prototypes.project_blueberry.entity.Fish.<init>(Fish.java:15)
    at com..prototypes.project_blueberry.Main.init(Main.java:56)
    at org.newdawn.slick.AppGameContainer.setup(AppGameContainer.java:393)
    at org.newdawn.slick.AppGameContainer.start(AppGameContainer.java:317)
    at com..prototypes.project_blueberry.Main.main(Main.java:44)

I have taken out some bits off stuff I don't want online, but the majority of stuff is there.

I have tried to troubleshoot the code, but I just can't figure out what is causing the exception. Any help? Thanks.

Answer 1

The problem here is that you haven't initialize the integer array in Misc.java class. If you need to store values into a integer array then you have to initialize it with a given size.

private static int[] ids = new int[10];