A DESCRIPTION OF THE PROBLEM :
The commands for running, creating the jar, and the manifest do not take into account the "misc" package.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The docs to properly list the "misc" package when needed:

java -splash:images/splash.gif misc.SplashDemo
java -splash:images/nnn.gif misc.SplashDemo

Main-Class: misc.SplashDemo

jar cmf splashmanifest.mf splashDemo.jar misc/SplashDemo*.class images/splash.gif
ACTUAL -
They are missing the misc package.

java -splash:images/splash.gif SplashDemo
java -splash:images/nnn.gif SplashDemo

Main-Class: SplashDemo

jar cmf splashmanifest.mf splashDemo.jar SplashDemo*.class images/splash.gif

URL OF FAULTY DOCUMENTATION :
https://docs.oracle.com/javase/tutorial/uiswing/misc/splashscreen.html