FULL PRODUCT VERSION :
java version "1.8.0_66"
Java(TM) SE Runtime Environment (build 1.8.0_66-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.66-b17, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Red Hat Enterprise Linux Workstation release 6.3

EXTRA RELEVANT SYSTEM CONFIGURATION :
Two monitors, X over TCP or ssh tunneling. KDE 4.10.5.

A DESCRIPTION OF THE PROBLEM :
Many Java applications when running in our network on desktops with two monitors are extremely slow in menu related operations. It takes 1 second to bring a popup a menu (top or seconday) and then 1 second to move from one menu item to another. I see similar problems not in menu, but in object built in JFXPanel. Context menu also has a delay.
Applications suffering from the issue are Oracle NetBeans, Oracle Solaris Studio, JetBrains Idea and Clion, Cadence tools. Eclipse is OK. Working with menus in NetBeans is practically impossible. It is not bearable.
It only happens over network and only with two monitors. It happens with X over tcp or with ssh tunneling.
There is a workaround but it is not free, that's why I think twice before starting a tool and before exiting.

It is possible that the issue is similar to what others saw
   http://stackoverflow.com/questions/26002948/workaround-for-slow-java-swing-menus

I ran wireshark on my X with one two monitors. With two monitors there are tons of X calls which are not present in one monitor configuration. These are GetProperty every 0.5ms, GetInputFocus every 0.5ms,
QueryTree every 1.5ms, GetWindowAttributes and GetGeometry every 0.5-1.5ms, GetInputFocus every 0.25ms. I must be impossible not to kill X in such a situation.

I have seen this problem for many years with different version of RHEL, from 5 (or even 4) to 6 and 7. I used a lot of versions of Java and SolStudio/Netbeans.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Start NetBeans.
Click on main menu.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
A popup must appear instantly.
ACTUAL -
There is one second delay before a popup appears.

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Open KDE System Settings, Display and Monitor.
Disable second monitor.
Start a Java program.
Enable second monitor.

Surprisingly, now the program works with menu very fast. Unfortunately, it is not very practical, because this sequence takes some time (not saying it is quite offensive to repeat it many times a day), all my windows now on one monitor, and mostly because sometimes I need to run my Java app from a debugger hundreds times a day. Disabling a monitor, enabling it back and sorting windows after that takes more than a minute.