The BFG is written in Scala, a modern functional language that runs on the JVM - so it can run anywhere Java can.

Here's a rough set of instructions for building the BFG, if you don't want to use the pre-built downloads:

• Install Java JDK 8 or above
• Install sbt
• git clone git@github.com:rtyley/bfg-repo-cleaner.git
• cd bfg-repo-cleaner
• sbt<- start the sbt console
• bfg/assembly <- download dependencies, run the tests, build the jar

To find the jar once it's built, just look at the last few lines of output from the assembly task - it'll say something like this:

[info] Packaging /Users/roberto/development/bfg-repo-cleaner/bfg/target/bfg-1.11.9-SNAPSHOT-master-21d2115.jar ...
[info] Done packaging.
[success] Total time: 19 s, completed 26-Sep-2014 16:05:11

If you're going to make changes to the Scala code, you may want to use IntelliJ and it's Scala plugin to help with the Scala syntax...!

If you use Eclipse IDE, you can set-up your development environment by following these instructions:

• Install sbt and build as-above
• Install Scala IDE for Eclipse into your Eclipse installation if not already installed
• Add the sbteclipse-plugin to your set of local sbt plugins:

mkdir -p ~/.sbt/1.0/plugins && tee ~/.sbt/1.0/plugins/plugins.sbt <<EOF
addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "5.2.2")
EOF

• sbt<- start the sbt console
• eclipse <- first-time only setup of the Eclipse plugin
• eclipse <- again, generate Eclipse project files (note that these are .gitignored)
• In Eclipse, File -> Import -> Existing Projects into Workspace, browse to your bfg working-copy, and ensure that you select Search for nested projects
• You should now have the 4 sbt projects imported into your Eclipse workspace.

I personally found Coursera's online Scala course very helpful in learning Scala, YMMV.