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
From the above comments, i tried this.
I added jfxrt.jar(Downloaded JDK) to PC. In eclipse, right click project --> properties --> Libraries --> Add external jar and choose the jar file.
The error went away.