The quickest way to learn how to use Hazelcast Jet is to start up a Jet cluster directly from your Java application and run some distributed data processing jobs. Check out the “Getting Started Guide.” Then we suggest you enroll for free Hazelcast training and take the “Stream Processing Essentials” course.
If you prefer learning by doing, we definitely recommend browsing the demo repository. Demos are self-contained and easy to run, so you can tweak and extend them. Demos are inspired by production Jet deployments.
Once you feel ready to begin looking at the wider set of features, there are extensive examples on github.