The atlas
Verified against Minecraft 26.3 · Maps · Four views of the whole decompile, drawn by
tools/map_source.pyfrom the source tree on every deploy.
Before any system page makes sense you want the answer to a newcomer’s question: where is everything? The atlas is that answer, looked at once. Each map is one or more figures drawn from the decompile, prose saying what they show, and the tables they were drawn from — four figures and two tables on what extends what, one and one on the two bar charts, one and three on where the code is. Take them in any order; none of the four needs another.
No number in the atlas’s figures and tables is counted by hand — they come
from tools/map_source.py, which reads all 7,301 files — but the four pages
are not all one thing, and the distinction matters as much here as on the
Reference shelf. The figures and the tables are
generated: they live in src/generated/, are rewritten on every deploy, and
cannot drift from the source they describe. The prose is typed, and every number quoted in a sentence was typed by a session, read
off one of those tables or counted from the tree where no table holds it. So a
version bump re-derives the tables by itself and leaves the sentences around
them to be re-read, which is what the version pass is for.
flowchart LR
D[("the 26.3 decompile")] --> T["map_source.py, on every deploy"] --> G["seven figures, seven tables"]
G -- "included as they are" --> P["the four map pages"]
G -- "read and typed by a session" --> S["the sentences"] --> P
D -. "or counted from it where no table holds the number" .-> S
The two routes into an atlas page: the figures and tables arrive by the upper one and cannot drift, and the sentences arrive by the lower one, typed by a session, which is the route a version bump has to walk again by hand.
The four maps
| map | the question it answers | the figure |
|---|---|---|
| Where the code is | how big is each package, which jar ships it, and which parts of the book cover it | the jar as a treemap of packages, area by lines |
| Where the mass is | which classes are the largest, and what kind of thing gets that big | the thirty largest classes as bars |
| What everything imports | which Mojang classes the rest of the code cannot be written without, and where the book teaches each | the thirty most-imported Mojang classes as bars |
| What extends what | which inheritance trees are widest, and what shape they are | four trees with the descendant count on every branch |
The treemap is also the book’s picture of the two jars: the introduction uses it to show how much of the code the dedicated server ships, and Part I’s what this book skips uses its hatching to draw the boundary of the book.
How the numbers are counted
The decompile is the client jar, which is a strict superset of the
server jar; beside it sits server-classes.txt, the list of classes the
dedicated server also ships. From those two things every number on these
pages follows.
| number | how it is counted |
|---|---|
| a class | one .java file in the decompile — nested types are not counted as classes, and the 565 four-line package-info.java markers are counted like any other file |
| a line | one line of the decompiled file, blank lines included, so counts are comparable with each other and not with Mojang’s own source |
| client-only | the file is not listed in server-classes.txt; shared means it is |
| fan-in | how many files have a net.minecraft or com.mojang import statement naming the class — the JDK is not counted, and same-package use needs no import, which is what what everything imports then has to allow for |
| descendants | every type reachable from a root through extends and implements, nested types included; a parent written as outer dot inner resolves inside the outer class’s own file, so two types with the same simple name stay two types |
The line counts include what the decompiler adds — braces on their own lines, expanded switches — and a table of constants written a line apiece can be longer than a class that does something. Read length as where the reading is, not where the difficulty is.
Rules: names, never code · how the system works, not how the code reads ·
newest version only · every backticked name passes tools/verify_names.py.