FULL PRODUCT VERSION :
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Windows 8.1

A DESCRIPTION OF THE PROBLEM :
When I try to execute a JavaFX application in a package from command line it doesn't work and it shows an error, "Error: Could not find or load main class pack.App.java" I used this command to execute the java class file :
java pack/App
But it doesn't work and it produced the above stated error.

REGRESSION. Last worked in version 8u91

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Step 1 : Make a JavaFX program inside a package
Step 2 : Compile and run that program using Command Line (CMD in Windows)
Step 3 : Use this command : java pack/App

Note: It works for all other applications other than JavaFX

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JavaFX Stage.
ACTUAL -
Error: Could not find or load main class pack.App.java

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Error: Could not find or load main class pack.App.java

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
This problem is with every JavaFX Application.
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
I solved this problem using : java pack.App

(Why is it not working with: java package/classname ?? As it works with every other Java program except JavaFX.

I think you should add this functionality as well to access it using package/classname. I found a solution by replacing the forward slash '/' with dot (.) and it worked.
Thanks !

SUPPORT :
YES