I just updated my JDK to the JDK 1.8 because i couldnt find the jfxrt.jar needed by java FX in the 1.7 version.
I downloaded the JDK from here: http://www.oracle.com/tec
You have to add requires jfxrt; to your module-info if you have trouble after adding jfxrt.jar
requires jfxrt;