Minimal working unsigned applet example.
The site's URL where the applet will get deployed needs to be whitelisted in the
Java control panel. Go to Java Control Panel > Security > Edit Site List and add
http://localhost:8000.
It's also useful to enable the Java console and logging. Go to Java Control Panel > Advanced and tick Enabled logging and select Show console.
After this when an applet starts a Java console will also start. Printing
something to System.out will end up here.
Execute ./gradlew run, which will build the project, copy my-applet.jar and
index.html under build/install/my-applet and serve that directory via HTTP
using python -m SimpleHTTPServer.
After this open http://localhost:8000 to see the applet in action or run
appletviewer http://localhost:8000. When the applet loads it should print
Hello World! to the console.