As a brief exercise I made a naïve solution for 24 Game. My first encounter with the puzzle was Maunulan pulmat (in Finnish). Result comes in Polish/prefix notation.

To run, you need Maven. (Maven setup adapted from kotlin-examples)

To execute:

mvn compile exec:java -Dexec.args="24.0 1.0 9.0 7.0 4.0"

To run the smoke tests:

mvn test