sos-java is based on IJava kernel, which in turn is based on JShell (https://docs.oracle.com/javase/9/jshell/introduction-jshell.htm#JSHEL-GUID-630F27C8-1195-4989-9F6B-2C51D46F52C8). JShell was introduced in Java 9.
To load a package, we use %jars
magic of IJava (https://github.com/SpencerPark/IJava/blob/master/docs/magics.md#jars)