Install Java 8:
https://www.azul.com/downloads/?version=java-8-lts&os=windows&architecture=x86-64-bit&package=jre&show-old-builds=true
Scroll down to 8u302b08 and install this build
Then open your start.bat and use:
"C:\Program Files\Zulu\zulu-8-jre\bin\javaw.exe" -Xmx8G -jar forge-server.jar
pause
Keep the quotation marks and make sure the forge server jar file name is matching