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# 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

<figure class="map">
*(figure: tree-Entity.svg — a generated SVG, not reproduced here)*
<figcaption>The <code>Entity</code> tree to three levels. The number is how many types descend from the node; subclasses with no subclasses of their own are folded into one italic line per parent, or named where a parent has only one. Click to enlarge.</figcaption>
</figure>

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](../systems/entities/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

<figure class="map">
*(figure: tree-Block.svg — a generated SVG, not reproduced here)*
<figcaption>The <code>Block</code> tree to three levels; 61 of its 92 direct subclasses have no subclasses of their own and are folded into the last line. Click to enlarge.</figcaption>
</figure>

`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](../systems/blocks/block-entities#create-keep-replace-remove)
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

<figure class="map">
*(figure: tree-Item.svg — a generated SVG, not reproduced here)*
<figcaption>The <code>Item</code> tree to three levels. Click to enlarge.</figcaption>
</figure>

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](../systems/items/items-and-stacks) is why the tree
is this shape.

## Screen

<figure class="map">
*(figure: tree-Screen.svg — a generated SVG, not reproduced here)*
<figcaption>The <code>Screen</code> tree to three levels; 59 of its 71 direct subclasses have no subclasses of their own. Click to enlarge.</figcaption>
</figure>

`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](../systems/client/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/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.

| root | descendants | direct | kind | where |
|---|---:|---:|---|---|
| `BlockBehaviour` | 298 | 1 | class | `net/minecraft/world/level/block/state` |
| `Block` | 297 | 92 | class | `net/minecraft/world/level/block` |
| `Goal` | 202 | 99 | class | `net/minecraft/world/entity/ai/goal` |
| `Entity` | 192 | 18 | class | `net/minecraft/world/entity` |
| `Model` | 170 | 14 | class | `net/minecraft/client/model` |
| `AbstractContainerEventHandler` | 162 | 1 | class | `net/minecraft/client/gui/components/events` |
| `Screen` | 161 | 71 | class | `net/minecraft/client/gui/screens` |
| `EntityModel` | 153 | 71 | class | `net/minecraft/client/model` |
| `EntityRenderer` | 133 | 28 | class | `net/minecraft/client/renderer/entity` |
| `LivingEntity` | 124 | 3 | class | `net/minecraft/world/entity` |
| `Mob` | 114 | 5 | class | `net/minecraft/world/entity` |
| `PathfinderMob` | 108 | 5 | class | `net/minecraft/world/entity` |
| `NamespacedSchema` | 107 | 107 | class | `net/minecraft/util/datafix/schemas` |
| `EntityRenderState` | 99 | 23 | class | `net/minecraft/client/renderer/entity/state` |
| `AbstractWidget` | 99 | 12 | class | `net/minecraft/client/gui/components` |
| `LivingEntityRenderer` | 96 | 3 | class | `net/minecraft/client/renderer/entity` |
| `MobRenderer` | 93 | 39 | class | `net/minecraft/client/renderer/entity` |
| `Particle` | 84 | 4 | class | `net/minecraft/client/particle` |
| `SingleQuadParticle` | 74 | 46 | class | `net/minecraft/client/particle` |
| `LivingEntityRenderState` | 70 | 44 | class | `net/minecraft/client/renderer/entity/state` |
| `Item` | 67 | 49 | class | `net/minecraft/world/item` |
| `BaseEntityBlock` | 64 | 40 | class | `net/minecraft/world/level/block` |
| `StructurePiece` | 63 | 8 | class | `net/minecraft/world/level/levelgen/structure` |
| `Entry` | 63 | 2 | class | `net/minecraft/client/gui/components` |
| `Behavior` | 58 | 53 | class | `net/minecraft/world/entity/ai/behavior` |
| `BlockEntity` | 52 | 35 | class | `net/minecraft/world/level/block/entity` |
| `AgeableMob` | 52 | 4 | class | `net/minecraft/world/entity` |
| `RenderLayer` | 48 | 39 | class | `net/minecraft/client/renderer/entity/layers` |
| `NamedEntityFix` | 47 | 47 | class | `net/minecraft/util/datafix/fixes` |
| `AgeableMobRenderer` | 45 | 26 | class | `net/minecraft/client/renderer/entity` |

| root | descendants | direct | kind | where |
|---|---:|---:|---|---|
| `FeatureElement` | 386 | 7 | interface | `net/minecraft/world/flag` |
| `ItemLike` | 366 | 2 | interface | `net/minecraft/world/level` |
| `TabOrderedElement` | 334 | 2 | interface | `net/minecraft/client/gui/components` |
| `GuiEventListener` | 332 | 5 | interface | `net/minecraft/client/gui/components/events` |
| `Renderable` | 269 | 6 | interface | `net/minecraft/client/gui/components` |
| `TypedInstance` | 252 | 5 | interface | `net/minecraft/core` |
| `DebugValueSource` | 248 | 3 | interface | `net/minecraft/util/debug` |
| `Packet` | 240 | 229 | interface | `net/minecraft/network/protocol` |
| `SlotProvider` | 231 | 2 | interface | `net/minecraft/world/entity` |
| `ContainerEventHandler` | 224 | 3 | interface | `net/minecraft/client/gui/components/events` |
| `Nameable` | 212 | 6 | interface | `net/minecraft/world` |
| `DataComponentGetter` | 200 | 4 | interface | `net/minecraft/core/component` |
| `ItemOwner` | 195 | 3 | interface | `net/minecraft/world/entity` |
| `UniquelyIdentifyable` | 194 | 1 | interface | `net/minecraft/world/level/entity` |
| `EntityAccess` | 193 | 1 | interface | `net/minecraft/world/level/entity` |
| `ScoreHolder` | 193 | 1 | interface | `net/minecraft/world/scores` |
| `SyncedDataHolder` | 193 | 1 | interface | `net/minecraft/network/syncher` |
| `Validatable` | 174 | 22 | interface | `net/minecraft/world/level/storage/loot` |
| `LayoutElement` | 173 | 4 | interface | `net/minecraft/client/gui/layouts` |
| `StringRepresentable` | 165 | 164 | interface | `net/minecraft/util` |
| `NarrationSupplier` | 146 | 3 | interface | `net/minecraft/client/gui/narration` |
| `Waypoint` | 131 | 2 | interface | `net/minecraft/world/waypoints` |
| `Attackable` | 126 | 2 | interface | `net/minecraft/world/entity` |
| `WaypointTransmitter` | 125 | 1 | interface | `net/minecraft/world/waypoints` |
| `Leashable` | 121 | 2 | interface | `net/minecraft/world/entity` |
| `ParticleProvider` | 119 | 114 | interface | `net/minecraft/client/particle` |
| `Targeting` | 116 | 2 | interface | `net/minecraft/world/entity` |
| `EquipmentUser` | 115 | 1 | interface | `net/minecraft/world/entity` |
| `NarratableEntry` | 103 | 2 | interface | `net/minecraft/client/gui/narration` |
| `RenderLayerParent` | 97 | 1 | interface | `net/minecraft/client/renderer/entity` |

---

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