Install · Emulators · Devices · Verification · Building · Development · Design

Building

Each game is an independent Ant project that shares the build logic in tools/ant/game-build.xml and the framework in common/src/gamekit. You can build one game or all 100.

Requirements

You do not need the Sun/Oracle Wireless Toolkit, ProGuard or a separate preverifier.

Toolchain

python tools/bootstrap.py downloads these into tools/lib/ and checks each file's SHA-256:

• Apache Ant 1.10.15
• Eclipse Compiler for Java (ECJ) 3.26.0
• CLDC 1.0 and MIDP 2.0 API stubs (org.microemu:cldcapi10 / midpapi20 2.0.4)
• MicroEmulator 2.0.4 (used only by tools/microemu_check.py)
• TeaVM 0.10.2 and its dependencies (used only for the browser demos; skip with --no-teavm)

How the MIDP build works

ECJ compiles each game with -source 1.3 -target cldc1.1 against the CLDC/MIDP stubs as the boot class path:

• -target cldc1.1 makes ECJ write Java 1.1-format class files (version 45.3) with the StackMap attribute that CLDC's split verifier needs. In other words the classes come out preverified, so no separate preverify step is needed.
• Compiling against the stubs instead of the JDK means any use of an API that a phone does not have (collections, String.format, floating point helpers, Integer.bitCount...) is a compile error.
• The JAD declares CLDC-1.0 and MIDP-2.0. The code uses no floating point, so CLDC 1.0 phones are supported.

The JAR is built with a fixed timestamp so rebuilds are byte-for-byte reproducible, and the JAD's MIDlet-Jar-Size is computed from the finished JAR.

Build commands

Linux / macOS / Git Bash:

python3 tools/bootstrap.py
tools/build-all.sh              # all games, in parallel (tools/build_all.py)
tools/build-all.sh --ant        # all games, sequentially with plain Ant
tools/build-game.sh 042         # one game
tools/build-game.sh 042 test    # one game + reference-runtime smoke test
tools/package.sh                # release/games/*.jar|jad + release/j2me-100-games-v1.0.0.zip

Windows (cmd or PowerShell):

python tools\bootstrap.py
tools\build-all.cmd
tools\build-game.cmd 042
tools\package.cmd

Plain Ant (after bootstrapping) from the repository root:

tools/ant.sh            # = ant dist
tools/ant.sh test       # build + reference-runtime test of every game
tools/ant.sh media      # screenshots and GIFs
tools/ant.sh web        # browser demos (needs a Java 17-21 runtime, see below)
tools/ant.sh package

Output for game NNN-slug is written to games/NNN-slug/dist/<Jar>.jar and <Jar>.jad.

Tests and validation

python tools/run_tests.py --jobs 8     # reference runtime, 5 screen sizes  -> reports/test-report.json
python tools/microemu_check.py         # MicroEmulator 2.0.4 smoke test     -> reports/microemu-report.json
python tools/validate.py               # repository checks                  -> reports/validation-report.md
python tools/gen_docs.py               # regenerate READMEs, docs/download.md, docs/verification.md

See verification.md for what each test does and does not prove.

Browser demos

tools/ant.sh web (or python tools/build_all.py --target web) compiles each game together with the reference runtime to JavaScript using TeaVM. TeaVM 0.10 cannot read JDK 22+ class files, so the TeaVM step runs on a separate Java 17-21 runtime: set TEAVM_JAVA=/path/to/java or unpack a JRE 21 into tools/jre21/. If your default java is already 17-21, nothing needs configuring.

Website

python tools/gen_docs.py
python tools/gen_site.py      # writes website/_site
python -m http.server -d website/_site 8000

Troubleshooting

Source: docs/building.md