ADDITIONAL SYSTEM INFORMATION :
Two screen setup, like laptop and external monitor or a beamer.

A DESCRIPTION OF THE PROBLEM :
Application started with JavaWebStart displays JMenu drop-down on wrong screen, if you extend your desktop by a second screen without restarting the JavaWebStart application.

I have already reported this behaviour in Bug 8187225. This was closed as dupliacte. And the related issue was solved and backported in Java8 U202(https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8207070)

But the bug still exists.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
You need two screens

1.Disconnect second screen, so that you have only one active ( "Windows + p" for windows disconnect)
2.Open web start from : https://docs.oracle.com/javase/tutorialJWS/samples/uiswing/ActionDemoProject/ActionDemo.jnlp
3.Click "Menu" all fine
4.Connect second screen ( "Windows + p" for windows) extended screen
5.Click "Menu" all fine
6.Move application window to second screen (on the screen which was active in step 2, where you started the application)
7.Click "Menu" => Items appear on wrong screen

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
I expected the same behaviour as in step 3. The MenuItems in step 7 should appear under the JMenu on the same screen as the application.
ACTUAL -
The application is displayed on one screen and the MenuItems popup appears on the other screen.

CUSTOMER SUBMITTED WORKAROUND :
Restart the JavaWebstart application always if you change your screen setup.

FREQUENCY : always