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

Running in an emulator

No phone? Any of these will run the JAR/JAD files. Each listing says honestly whether the maintainers have run the games with that emulator.

Reports for the untested emulators are welcome: open an issue with the result.

MicroEmulator (desktop)

MicroEmulator is a Java SE implementation of MIDP 2.0. Version 2.0.4 is on Maven Central; the bootstrap script downloads it to tools/lib/microemu/microemulator-2.0.4.jar.

Interactive window:

java -jar tools/lib/microemu/microemulator-2.0.4.jar games/001-retro-snake/dist/RetroSnake.jad

Then use the on-screen keypad or your keyboard (number keys, arrow keys, Enter for fire). MicroEmulator is old; if the window misbehaves on a new JDK, run it with a Java 8-21 runtime.

Headless smoke test of every game, as the project's CI does:

python tools/bootstrap.py --no-teavm
tools/build-all.sh
python tools/microemu_check.py --jobs 4

MicroEmulator's URL handling breaks on paths with spaces. The check script copies each game to a temporary folder first; do the same if you launch it by hand.

J2ME Loader (Android)

1. Install J2ME Loader from F-Droid or the Play Store.
2. Copy the .jar to the Android device.
3. In J2ME Loader tap +, pick the JAR, and adjust screen size if you like (176x208 or 240x320 are good choices).
4. Use the on-screen keypad. The * key pauses; 5 is fire.

KEmulator (Windows)

Open KEmulator, choose Midlet > Load jar, and pick the JAR. Set the screen size under View > Options (try 176x220 or 240x320).

FreeJ2ME

java -jar freej2me.jar file:///path/to/RetroSnake.jar 240 320

Oracle Java ME SDK / Sun Wireless Toolkit

Choose File > Open JAD, pick the JAD, and run it on the DefaultColorPhone skin (240x320) or QwertyDevice.

Project reference runtime

The project includes its own small MIDP implementation (emu/core) used for automated testing and, compiled to JavaScript, for the browser demos. It is a test tool and not a full emulator, but you can use it to capture screenshots:

java -cp tools/build/emu-desktop.jar emu.desktop.Harness --jad games/001-retro-snake/dist/RetroSnake.jad \
     --out /tmp/shots --sizes 240x320 --script "w500 shot:title 5 w2000 shot:play"

Key mapping reminders

Source: docs/emulator.md