The JavaFX Deployment Guide was updated for the JavaFX 2.2.40 release to describe the new User JVM Arguments in the Ant tasks. Now you can create applications that allow users to override jvm options. For example, users can change the heap size for the application.
<fx:jvmuserarg> attribute has been added to
<fx:platform>. This new attribute explicitly defines an attribute that can be overridden by users. For instance:
<fx:jvmuserarg name="-Xmx" value="768m" />
For this specific case,
-Xmx768m is passed as a default value for the heap size. The user can override this value in a user configuration file (on Linux and Mac) or in the registry in Windows.
For more information see the Deploying JavaFX Applications guide.