So I am attempting to add a right click interaction on my JellyfishEntity that when a bottle is being held it will result in Jellyfish Jelly. I practically just copied the Cow milk interaction and the only issue I am having is that the method requires an ItemStack however I am unsure as how to convert my item registry into that.
 

This is in the entity:

    public InteractionResult mobInteract(Player p_28298_, InteractionHand p_28299_) {
        ItemStack itemstack = p_28298_.getItemInHand(p_28299_);
        if (itemstack.is(Items.GLASS_BOTTLE) && !this.isBaby()) {
           p_28298_.playSound(SoundEvents.COW_MILK, 1.0F, 1.0F);
           ItemStack itemstack1 = ItemUtils.createFilledResult(itemstack, p_28298_, ModItems.JELLYFISH_JELLY.getDefaultInstance());
           p_28298_.setItemInHand(p_28299_, itemstack1);
           return InteractionResult.sidedSuccess(this.level.isClientSide);
        } else {
           return super.mobInteract(p_28298_, p_28299_);
        }
    }

And this is my Item:

    public static final RegistryObject<Item> JELLYFISH_JELLY = ITEMS.register("jellyfish_jelly", 
        () -> new JellyfishJellyItem(new Item.Properties().craftRemainder(Items.GLASS_BOTTLE).tab(ModCreativeModeTab.GODBOB_TAB)));

The only issue seems to be with the

ModItems.JELLYFISH_JELLY.getDefaultInstance()

It was originally:

Items.MILK_BUCKET.getDefaultInstance()

Thanks in advance.

I think what you want is 

new ItemStack(ModItems.JELLYFISH_JELLY.getDefaultInstance())

 

8 minutes ago, h3tR said:

I think what you want is 

new ItemStack(ModItems.JELLYFISH_JELLY.getDefaultInstance())

 

It still gives me

The method getDefaultInstance() is undefined for the type RegistryObject<Item>

When using that though...

Your JELLYFISH_JELLY is a RegistryObject<Item> not an Item.

You need to use get() to obtain the real registered object.

ModItems.JELLYFISH_JELLY.get().getDefaultInstance()

https://forge.gemwire.uk/wiki/Registration

6 minutes ago, warjort said:

Your JELLYFISH_JELLY is a RegistryObject<Item> not an Item.

You need to use get() to obtain the real registered object.

ModItems.JELLYFISH_JELLY.get().getDefaultInstance()

https://forge.gemwire.uk/wiki/Registration

Ah I see, thank you!