ExampleMod.java

package com.example.examplemod;

import net.fabricmc.api.ModInitializer;
import net.fabricmc.fabric.api.itemgroup.v1.ItemGroupEvents;
import net.fabricmc.fabric.api.object.builder.v1.block.FabricBlockSettings;
import net.minecraft.block.Block;
import net.minecraft.block.AbstractBlock;
import net.minecraft.item.Item;
import net.minecraft.item.ItemGroups;
import net.minecraft.item.ItemStack;
import net.minecraft.registry.Registries;
import net.minecraft.registry.Registry;
import net.minecraft.registry.RegistryKey;
import net.minecraft.registry.RegistryKeys;
import net.minecraft.util.Identifier;

/**
 * Entry point. Registered in fabric.mod.json under "entrypoints" -> "main".
 * Works unchanged across 1.21.7 - 1.21.11; registry/item APIs have been
 * stable through this range.
 */
public class ExampleMod implements ModInitializer {

    public static final String MOD_ID = "examplemod";

    // --- Item registration (key-first pattern, current best practice) ---
    public static final Item EXAMPLE_GEM = registerItem(
            "example_gem",
            settings -> new Item(settings)
    );

    // --- Block registration ---
    public static final Block EXAMPLE_BLOCK = registerBlock(
            "example_block",
            settings -> new Block(settings),
            AbstractBlock.Settings.create().strength(4.0f).requiresTool()
    );

    @Override
    public void onInitialize() {
        // Add our gem to the "ingredients" creative tab
        ItemGroupEvents.modifyEntriesEvent(ItemGroups.INGREDIENTS).register(entries ->
                entries.add(EXAMPLE_GEM)
        );

        // Add a BlockItem for our block so it shows up in the building blocks tab
        ItemGroupEvents.modifyEntriesEvent(ItemGroups.BUILDING_BLOCKS).register(entries ->
                entries.add(new ItemStack(EXAMPLE_BLOCK))
        );
    }

    private static Item registerItem(String path, java.util.function.Function<Item.Settings, Item> factory) {
        RegistryKey<Item> key = RegistryKey.of(RegistryKeys.ITEM, Identifier.of(MOD_ID, path));
        Item item = factory.apply(new Item.Settings().registryKey(key));
        return Registry.register(Registries.ITEM, key, item);
    }

    private static Block registerBlock(String path,
                                        java.util.function.Function<AbstractBlock.Settings, Block> factory,
                                        AbstractBlock.Settings settings) {
        RegistryKey<Block> key = RegistryKey.of(RegistryKeys.BLOCK, Identifier.of(MOD_ID, path));
        Block block = factory.apply(settings.registryKey(key));
        return Registry.register(Registries.BLOCK, key, block);
    }
}