public class ExampleMod implements ModInitializer {

    // For versions before 1.21, replace `Identifier.of` with `new Identifier`.
    public static final Block BOX_BLOCK = Registry.register(Registries.BLOCK, Identifier.of("tutorial", "box_block"),
        new BoxBlock(AbstractBlock.Settings.copyOf(Blocks.CHEST)));
        
    public static final BlockItem BOX_BLOCK_ITEM = Registry.register(Registries.ITEM, Identifier.of("tutorial", "block"),
        new BlockItem(BOX_BLOCK, new Item.Settings()));
        
    public static final BlockEntityType<BoxBlockEntity> BOX_BLOCK_ENTITY = Registry.register(Registry.BLOCK_ENTITY_TYPE, Identifier.of("tutorial", "box_block"), 
        BlockEntityType.Builder.create(BoxBlockEntity::new, BOX_BLOCK).build());
    // In 1.17 use FabricBlockEntityTypeBuilder instead of BlockEntityType.Builder
    // public static final BlockEntityType<BoxBlockEntity> BOX_BLOCK_ENTITY = Registry.register(Registry.BLOCK_ENTITY_TYPE, new Identifier("tutorial", "box_block"),
    //     FabricBlockEntityTypeBuilder.create(BoxBlockEntity::new, BOX_BLOCK).build(null));;

    @Override
    public void onInitialize() {
    }
}