Mod Items

ModItems.java

package jprugel.sera.item;

import jprugel.sera.Sera;
import net.minecraft.item.Item;
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;

import java.util.function.Function;

public class ModItems {
    public static final Item VAULT_LOCK = register("vault_lock", VaultLockItem::new, new Item.Settings());

    public static void initialize() {

    }

    public static Item register(String name, Function<Item.Settings, Item> itemFactory, Item.Settings settings) {
        // Create the item key.
        RegistryKey<Item> itemKey = RegistryKey.of(RegistryKeys.ITEM, Identifier.of(Sera.MOD_ID, name));

        // Create the item instance.
        Item item = itemFactory.apply(settings.registryKey(itemKey));

        // Register the item.
        Registry.register(Registries.ITEM, itemKey, item);

        return item;
    }
}

VaultLockItem.java

package jprugel.sera.item;

import eu.pb4.polymer.core.api.item.PolymerItem;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.item.Items;
import xyz.nucleoid.packettweaker.PacketContext;

public class VaultLockItem extends Item implements PolymerItem {
    public VaultLockItem(Settings settings) {
        super(settings);
    }

    @Override
    public Item getPolymerItem(ItemStack itemStack, PacketContext packetContext) {
        return Items.BOOK;
    }
}