Awesome

Coffee GB

Coffee GB is a Gameboy Color emulator written in Java 8. It's meant to be a development exercise. More info can be found in the blog post Why did I spend 1.5 months creating a Gameboy emulator?

Coffee GB running game

The emulator can be build with Maven:

mvn clean package

The coffee-gb-*-complete.jar executable file will be available in the ./target directory.

Play with <kbd>←</kbd>, <kbd>↑</kbd>, <kbd>↓</kbd>, <kbd>→</kbd>, <kbd>Z</kbd>, <kbd>X</kbd>, <kbd>Enter</kbd>, <kbd>Backspace</kbd>.

Cycle-exact Gameboy CPU emulation. Each opcode is split into a few micro-operations (load value from memory, store it to register, etc.) and each micro-operation is run in a separate CPU cycle.
Quite compatible (all the Blargg's tests are passed, although some game still doesn't work)
GPU
Joypad
Timer
Sound
MBC1-5 support
Battery saves
Support for zipped ROMs
ROM-based compatibility tests run from Maven

The Blargg's test ROMs are used for testing the compatibility. Tests can be launched from Maven using appropriate profile:

mvn clean test -Ptest-blargg
mvn clean test -Ptest-blargg-individual # for running "single" tests providing more diagnostic info

They are also part of the Travis-based CI.

The tests output (normally displayed on the Gameboy screen) is redirected to the stdout:

cpu_instrs

01:ok  02:ok  03:ok  04:ok  05:ok  06:ok  07:ok  08:ok  09:ok  10:ok  11:ok

Passed all tests

Coffee GB passes all the tests:

The Mooneye GB emulator comes with a great set of test ROMs. They can be used to test the Coffee GB as well. Use -Ptest-mooneye profile:

mvn clean test -Ptest-mooneye

Coffee GB running game

The default key bindings can be changed with the ~/.coffeegb.properties file. The file has following format:

btn_up=VK_UP
btn_down=VK_DOWN
btn_left=VK_LEFT
btn_right=VK_RIGHT
btn_a=VK_Z
btn_b=VK_X
btn_start=VK_ENTER
btn_select=VK_BACK_SPACE

The key list can be found in the KeyEvent JavaDoc.