Main Class

package com.author.example;

import com.author.example.lists.BlockList;
import com.author.example.lists.FluidList;
import com.author.example.lists.ItemList;
import com.author.example.lists.PotionList;
import net.minecraft.client.renderer.RenderType;
import net.minecraft.client.renderer.RenderTypeLookup;
import net.minecraft.item.BlockItem;
import net.minecraft.item.Item;
import net.minecraft.item.ItemGroup;
import net.minecraft.item.ItemStack;
import net.minecraftforge.event.RegistryEvent;
import net.minecraftforge.eventbus.api.IEventBus;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import net.minecraftforge.fml.RegistryObject;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent;
import net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent;
import net.minecraftforge.fml.event.server.FMLServerStartingEvent;
import net.minecraftforge.fml.javafmlmod.FMLJavaModLoadingContext;
import net.minecraftforge.registries.IForgeRegistry;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

@Mod(Main.MOD_ID)
@Mod.EventBusSubscriber(modid = Main.MOD_ID)
public class Main {

    public static Main instance;
    public static final String MOD_ID = "example";
    public static final ItemGroup EXAMPLE_TAB = new Main.ExampleItemGroup("example_group");
    public static final Logger LOGGER = LogManager.getLogger();

    public Main() {
        instance = this;

        final IEventBus modEventBus = FMLJavaModLoadingContext.get().getModEventBus();

        modEventBus.addListener(this::setup);
        modEventBus.addListener(this::clientSetup);

        ItemList.ITEMS.register(modEventBus);
        FluidList.FLUIDS.register(modEventBus);
        BlockList.BLOCKS.register(modEventBus);
        BlockList.BLOCKS_NO_ITEM.register(modEventBus);
        PotionList.EFFECTS.register(modEventBus);
        PotionList.POTIONS.register(modEventBus);
    }

    @SubscribeEvent
    public static void createBlockItems(final RegistryEvent.Register<Item> event) {

        final IForgeRegistry<Item> registry = event.getRegistry();

        BlockList.BLOCKS.getEntries().stream().map(RegistryObject::get).forEach(block -> {

            final Item.Properties properties = new Item.Properties().group(EXAMPLE_TAB);
            final BlockItem blockItem = new BlockItem(block, properties);
            blockItem.setRegistryName(block.getRegistryName());
            registry.register(blockItem);
        });
    }

    private void setup(final FMLCommonSetupEvent event) {
        PotionList.addBrewingRecipes();
    }

    private void clientSetup(final FMLClientSetupEvent event) {
        RenderTypeLookup.setRenderLayer(BlockList.MOD_CROP.get(), RenderType.getCutout());
        RenderTypeLookup.setRenderLayer(BlockList.MOD_BERRY_BUSH.get(), RenderType.getCutout());
    }

    public void onServerStarting(FMLServerStartingEvent event) {

    }

    public static class ExampleItemGroup extends ItemGroup {

        public ExampleItemGroup(String name) {
            super(name);
        }

        @Override
        public ItemStack createIcon() {
            return new ItemStack(ItemList.MOD_CROP.get());
        }
    }
}