This is the dedicated public example for the shipped SDKMAN-backed Java toolchain boundary.

Use it when the repo wants toolchains.java to own java and javac, while Maven stays explicit under tools.

• toolchains.java is the owner for the managed Java runtime and javac
• toolchains.java.fulfillment separates Java capability truth from fulfillment truth
• fulfillment.source: sdkman is the canonical public way to say the selected path should use SDKMAN-backed fulfillment
• requirements.toolchains selects the Java runtime lane for the chosen task path
• Maven should stay under tools.maven because the Java toolchain does not own it in v1
• runtimes.java, tools.java, and tools.javac should not be declared alongside toolchains.java

Rust proves the richer managed-surface shape and Node proves the narrower Corepack shape. This example teaches the Java boundary directly:

• one Java toolchain owner
• one standalone Maven tool lane
• one selected-path contract that keeps those owners separate

Inspect the contract first:

ota validate .
ota doctor .
ota up --dry-run .
ota tasks --use .

Use ota tasks --use . to inspect the runnable task surface before execution: command preview, mode selection, safety posture, declared effects, and the matching dry-run / receipt follow-up commands stay visible in one place.

Then compare the selected task paths:

ota run build
ota run test

• ota doctor should diagnose Java through toolchains.java
• ota up --dry-run should show toolchains.java through structured fulfillment and keep Maven separate as a standalone tool requirement
• ota run build and ota run test should require both the Java toolchain and Maven
• ota should reject duplicate runtimes.java, tools.java, or tools.javac declarations

• Java repos that currently hide SDKMAN or JDK setup in shell scripts
• repos that want one clear Java owner without pretending Maven belongs to the toolchain
• teams that need one copyable example for the shipped Java toolchain surface