What extends what

Verified against Minecraft 26.3 · Maps · The widest inheritance trees, four of them drawn with the number of descendants on every branch.

Block has 297 descendants and Entity 192 — descendants, not direct subclasses, which is the count both tables below use — and those are the two trees a reader of this book will climb most often. But neither is the widest hierarchy in the game. That is FeatureElement, with 386 descendants from seven implementers — and it is not a hierarchy at all. It is an interface for anything that can be put behind a feature flag, and its seven implementers are BlockBehaviour, Item, EntityType, MenuType, MobEffect, Potion and GameRule, so its descendant count sweeps up the whole block tree and the whole item tree at once. ItemLike, second at 366, is Block plus Item. The interface table is a list of which mix-ins reach furthest; the class table is where the real trees are, and four of them are drawn below.

Entity

The shape is a spine with a few branches. LivingEntity holds 124 of the 192, Mob 114 of those, PathfinderMob 108 of those: nearly every mob is four classes deep before it is a species, and Part VI’s entity anatomy is that spine. The non-living entities are two families and a scattering — Projectile (26) and VehicleEntity (15), then hanging things, displays, and thirteen direct subclasses of Entity with no children of their own, from ItemEntity to LightningBolt.

Block

Block is wide and shallow: 92 direct subclasses, most of them terminal. The one deep branch is BaseEntityBlock (64), the abstract base most of the blocks that own a block entity extend — the interface that actually decides is EntityBlock, and two blocks implement it without taking that base at all, ComparatorBlock and JigsawBlock. Part V’s block entities is the branch in prose. The table’s first row, BlockBehaviour at 298, is the same tree seen from one class higher — Block is its only subclass, and it exists so that a block’s behaviour and its registry identity can be separate classes.

Item

Sixty-seven types descend from Item, for over a thousand registered items. The tree is small because an item’s behaviour mostly is not in its class: what a stack does is in its data components, and Items registers most of the game as a plain Item or BlockItem with an Item.Properties describing it. Part VII’s items and stacks is why the tree is this shape.

Screen

Screen (161) is Block’s shape again — 71 direct subclasses, 59 of them terminal — with one deep branch, AbstractContainerScreen (27), the screens that show a menu (GUI and screens is Part X’s), and one branch that is not in this book, RealmsScreen (27). The row above it in the table, AbstractContainerEventHandler at 162, is Screen’s parent with Screen as its only subclass, the same one-class-higher effect as BlockBehaviour.

Two trees the table shows and the figures do not

Goal has 202 descendants from 99 direct subclasses, and 132 of the 202 are nested classes, all but one inside the mob they serve — a fox’s own goals are declared in Fox, not in world/entity/ai/goal. Packet is an interface with 240 descendants from 229 direct implementers, and almost nothing below them: the packet catalogue is flat, and the packets reference is its list.

The tables

Class roots first, then interface roots; each table is the thirty roots of its kind with the most descendants. direct is the number of immediate subclasses or implementers; where is the package of the root.

Rules: names, never code · how the system works, not how the code reads · newest version only · every backticked name passes tools/verify_names.py.