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# Where the mass is

> Verified against **Minecraft 26.3** · Maps · The forty largest classes by lines of decompiled source, the top thirty of them drawn, coloured by which jar ships them.

The two largest classes in the game are the top of one hierarchy: `Entity`
and `LivingEntity`, 9,078 lines between them, the thing every mob and
player is before it is anything else. Third is `Minecraft`, the client
itself. And then the list turns odd: two of the top ten are not game logic
at all. `BlockModelGenerators` runs only inside the data generator — its
single caller is `ModelProvider` — and writes the block model JSON that ships
in the jar; `BlockStateData` is a table that the save-migration fixes consult
when data a much older version saved is read, and nothing outside
`util/datafix` reads it. Size is where the reading is,
not where the game is.

<figure class="map">
*(figure: biggest.svg — a generated SVG on the site; its data follows)*

| class | lines | side |
|---|---:|---|
| `net/minecraft/world/entity/Entity` | 4,617 | shared |
| `net/minecraft/world/entity/LivingEntity` | 4,461 | shared |
| `net/minecraft/client/Minecraft` | 3,345 | client |
| `net/minecraft/client/data/models/BlockModelGenerators` | 3,136 | client |
| `net/minecraft/client/multiplayer/ClientPacketListener` | 3,090 | client |
| `net/minecraft/server/MinecraftServer` | 2,608 | shared |
| `net/minecraft/server/network/ServerGamePacketListenerImpl` | 2,567 | shared |
| `net/minecraft/server/level/ServerPlayer` | 2,516 | shared |
| `net/minecraft/util/datafix/fixes/BlockStateData` | 2,270 | shared |
| `net/minecraft/server/level/ServerLevel` | 2,139 | shared |
| `net/minecraft/world/item/Items` | 2,067 | shared |
| `net/minecraft/world/level/block/Blocks` | 2,061 | shared |
| `net/minecraft/world/entity/player/Player` | 2,034 | shared |
| `net/minecraft/sounds/SoundEvents` | 2,023 | shared |
| `net/minecraft/client/Options` | 2,010 | client |
| `net/minecraft/world/level/levelgen/structure/structures/OceanMonumentPieces` | 1,983 | shared |
| `net/minecraft/world/item/CreativeModeTabs` | 1,737 | shared |
| `net/minecraft/server/level/ChunkMap` | 1,661 | shared |
| `net/minecraft/util/datafix/DataFixers` | 1,637 | shared |
| `net/minecraft/world/entity/animal/fox/Fox` | 1,625 | shared |
| `net/minecraft/world/entity/Mob` | 1,616 | shared |
| `net/minecraft/client/renderer/LevelRenderer` | 1,499 | client |
| `net/minecraft/client/gui/Hud` | 1,481 | client |
| `net/minecraft/world/entity/animal/bee/Bee` | 1,450 | shared |
| `net/minecraft/world/level/levelgen/structure/structures/StrongholdPieces` | 1,436 | shared |
| `net/minecraft/client/player/LocalPlayer` | 1,435 | client |
| `net/minecraft/network/FriendlyByteBuf` | 1,414 | shared |
| `net/minecraft/data/loot/packs/VanillaBlockLoot` | 1,412 | shared |
| `net/minecraft/world/level/block/state/BlockBehaviour` | 1,380 | shared |
| `net/minecraft/util/Util` | 1,372 | shared |
| `net/minecraft/gametest/framework/GameTestHelper` | 1,369 | shared |
| `com/mojang/realmsclient/RealmsMainScreen` | 1,344 | client |
| `net/minecraft/client/multiplayer/ClientLevel` | 1,334 | client |
| `net/minecraft/world/level/levelgen/structure/structures/NetherFortressPieces` | 1,317 | shared |
| `net/minecraft/world/item/ItemStack` | 1,274 | shared |
| `net/minecraft/world/level/levelgen/structure/structures/WoodlandMansionPieces` | 1,185 | shared |
| `net/minecraft/world/entity/animal/panda/Panda` | 1,121 | shared |
| `net/minecraft/world/entity/animal/equine/AbstractHorse` | 1,115 | shared |
| `net/minecraft/client/gui/screens/inventory/CreativeModeInventoryScreen` | 1,107 | client |
| `net/minecraft/world/entity/monster/cubemob/SulfurCube` | 1,083 | shared |
<figcaption>The thirty largest classes of 26.3. Blue ships in both jars, orange is client-only; the small grey text is the package under <code>net/minecraft</code>, or under <code>com/mojang</code> where it starts <code>mojang/</code>. Click to enlarge.</figcaption>
</figure>

**64,082 lines** are in these thirty classes, 8.6% of the game in 0.4% of
its files.

## Three kinds of big

Read down the bars and twenty-four of the thirty sort themselves into three
kinds, and the kind tells you how to read the class.

**The god objects.** `Entity` and `LivingEntity` are the trunk, each over four
thousand lines because each is the base of everything below it. The
fork below them is not one chain: `Mob` is one of `LivingEntity`'s direct
subclasses and `Avatar` is another, with `Player` under it
and `ServerPlayer` and `LocalPlayer` its two leaves in the thirty
([entity anatomy](../systems/entities/entity-anatomy) has the tree). Those
two leaves are long for the opposite reason to the trunk: no named class
descends from either, and each is a whole side of the authority split written out.
`Minecraft` and `MinecraftServer` are the two programs' roots; `ServerLevel`
is the world; `ChunkMap` is the world's loader. Only two concrete mobs make
the thirty — `Fox` and `Bee`, the two with the most bespoke behaviour in their own files — and
what they are long *with* is per-species goal classes, which is exactly why
[Part VI](../systems/entities/README) explains the machine and declines to
enumerate its instances: there is no `Fox` page and there is not going to be
one.

**The switchboards.** `ClientPacketListener` is a handler method for every
clientbound play packet, and `ServerGamePacketListenerImpl` is the same for
every serverbound one — all but three of the packets both phases share are
handled one class up, in `ClientCommonPacketListenerImpl` and
`ServerCommonPacketListenerImpl`; between them they are the whole of what play
can say, which is why Part IX's pages keep coming back to them.
`FriendlyByteBuf` is the buffer their packets are read from.

**The catalogues written as code.** `SoundEvents`, `Blocks` and `Items` are
registries populated a constant at a time, and `CreativeModeTabs` lists every
tab's items a line apiece;
`DataFixers` is the migration history; `OceanMonumentPieces` and `StrongholdPieces` are
structures built by hand, room by room, in Java rather than in a template;
`Options` is every setting in *options.txt*, and `Hud` is the in-world overlay
— the crosshair, the hotbar, the bars — inside the wider `Gui` that also
draws screens, toasts and the loading overlay. These are long because they are lists. None is hard.

## The table

Forty rows, of which the figure draws thirty. *side* is which jar ships
the class.

| class | lines | side |
|---|---:|---|
| `net/minecraft/world/entity/Entity` | 4,617 | shared |
| `net/minecraft/world/entity/LivingEntity` | 4,461 | shared |
| `net/minecraft/client/Minecraft` | 3,345 | client |
| `net/minecraft/client/data/models/BlockModelGenerators` | 3,136 | client |
| `net/minecraft/client/multiplayer/ClientPacketListener` | 3,090 | client |
| `net/minecraft/server/MinecraftServer` | 2,608 | shared |
| `net/minecraft/server/network/ServerGamePacketListenerImpl` | 2,567 | shared |
| `net/minecraft/server/level/ServerPlayer` | 2,516 | shared |
| `net/minecraft/util/datafix/fixes/BlockStateData` | 2,270 | shared |
| `net/minecraft/server/level/ServerLevel` | 2,139 | shared |
| `net/minecraft/world/item/Items` | 2,067 | shared |
| `net/minecraft/world/level/block/Blocks` | 2,061 | shared |
| `net/minecraft/world/entity/player/Player` | 2,034 | shared |
| `net/minecraft/sounds/SoundEvents` | 2,023 | shared |
| `net/minecraft/client/Options` | 2,010 | client |
| `net/minecraft/world/level/levelgen/structure/structures/OceanMonumentPieces` | 1,983 | shared |
| `net/minecraft/world/item/CreativeModeTabs` | 1,737 | shared |
| `net/minecraft/server/level/ChunkMap` | 1,661 | shared |
| `net/minecraft/util/datafix/DataFixers` | 1,637 | shared |
| `net/minecraft/world/entity/animal/fox/Fox` | 1,625 | shared |
| `net/minecraft/world/entity/Mob` | 1,616 | shared |
| `net/minecraft/client/renderer/LevelRenderer` | 1,499 | client |
| `net/minecraft/client/gui/Hud` | 1,481 | client |
| `net/minecraft/world/entity/animal/bee/Bee` | 1,450 | shared |
| `net/minecraft/world/level/levelgen/structure/structures/StrongholdPieces` | 1,436 | shared |
| `net/minecraft/client/player/LocalPlayer` | 1,435 | client |
| `net/minecraft/network/FriendlyByteBuf` | 1,414 | shared |
| `net/minecraft/data/loot/packs/VanillaBlockLoot` | 1,412 | shared |
| `net/minecraft/world/level/block/state/BlockBehaviour` | 1,380 | shared |
| `net/minecraft/util/Util` | 1,372 | shared |
| `net/minecraft/gametest/framework/GameTestHelper` | 1,369 | shared |
| `com/mojang/realmsclient/RealmsMainScreen` | 1,344 | client |
| `net/minecraft/client/multiplayer/ClientLevel` | 1,334 | client |
| `net/minecraft/world/level/levelgen/structure/structures/NetherFortressPieces` | 1,317 | shared |
| `net/minecraft/world/item/ItemStack` | 1,274 | shared |
| `net/minecraft/world/level/levelgen/structure/structures/WoodlandMansionPieces` | 1,185 | shared |
| `net/minecraft/world/entity/animal/panda/Panda` | 1,121 | shared |
| `net/minecraft/world/entity/animal/equine/AbstractHorse` | 1,115 | shared |
| `net/minecraft/client/gui/screens/inventory/CreativeModeInventoryScreen` | 1,107 | client |
| `net/minecraft/world/entity/monster/cubemob/SulfurCube` | 1,083 | shared |

---

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