Here is my code for registering my items. Does anything stand out that may prevent the items from being sorted properly? The items are being set to the creative tab in their constructors.

 

public static void registerItems() {
        registerItem(new ItemParticleBase("CreativeTabItem").setCreativeTab(null));

        registerItem(new ItemParticleBase("Air"));
        registerItem(new ItemParticleBase("Water"));
        registerItem(new ItemParticleBase("Fire"));
        registerItem(new ItemParticleBase("Earth"));
        registerItem(new ItemParticleBase("Light"));
        registerItem(new ItemParticleBase("Energy"));

        registerItem(new ItemBindingAgentBase("Level1"));
        registerItem(new ItemBindingAgentBase("Level2"));
        registerItem(new ItemBindingAgentBase("Level3"));
        registerItem(new ItemBindingAgentBase("Level4"));
        registerItem(new ItemBindingAgentBase("Level5"));
    }

    public static void registerItem(Item item) {
        GameRegistry.register(item);
    }

Items are sorted by ID in the creative tab and that order is (more or less) random.

See my tutorial if you want to enforce a specific order.

 

I followed your tutorial, but it crashes every time I try to open the tab. Here is my current code:

        @Override
        public void displayAllRelevantItems(List<ItemStack> items) {
            super.displayAllRelevantItems(items);
            //Collections.sort(items, comparator);
        }

...

    public static Comparator<ItemStack> comparator = Ordering.explicit(ItemRegistry.creativeTabList).onResultOf(new Function<ItemStack, Item>() {
        @Override
        public Item apply(ItemStack input) {
            return input.getItem();
        }
    });

 

Here is the crash:

 

Time: 6/8/16 8:54 PM
Description: Updating screen events

com.google.common.collect.Ordering$IncomparableValueException: Cannot compare value: src.gamrcorps.particlesmod.item.particle.ItemParticleBase@11742b4f

You should add every items that can be displayed on the creative tab.

Found the problem, just had to make sure that the list was filled before creating the comparator.