This error may occur when you run AEM 6.0 with Java 8. Java version 8, is not supported with AEM 6.0 until you install the service pack. If you are having that problem, install the service pack. You can follow these steps:
Once downloaded, go to the folder where you installed AEM initially, and delete all the contents in the crx-quickstart folder (you will be running a fresh install) so you will now have an empty crx-quickstart folder.
In the crx-quickstart folder, create a new folder called install and copy the service pack that you downloaded to that folder.
The structure should now be: crx-quickstart > install > ServicePack2.zip
Start AEM by double clicking the AEM quickstart jar, and when it starts, it will find the install folder and also install the Service Pack.