How to get the content scale factor (hiDPI) on Mac on OpenJDK8?

[Tobias Bley]

With Apple JDK6 we can call the scale factor like this: 
toolkit.getDesktopProperty("apple.awt.contentScaleFactor“);

Unfortunately thats not possible with JDK7/8. Is there another way to get the 
scale factor?

Best regards,
Tobi