Project Page: http://maxcamillo.github.io/android-keystore-password-recover/
Make sure you have the Java SDK installed. Google it for install files and usage instructions.
Then to build, execute this:
javac -d ./build *.java
Then to package that into a JAR execute this:
cd build
jar cvfm akpr.jar ../manifest.mf AndroidKeystoreBrute/*.class
To run:
java -jar akpr.jar