Is jdk 1.8 is required for Appian 7.9 and EAP Jboss 6.3 ?

Have a look at - forum.appian.com/.../System_Requirements.html

Got an error when running configure.bat.

Exception in thread "main" java.lang.UnsupportedClassVersionError: com/appian/configure/Me
nu : Unsupported major.minor version 52.0

Make sure the environment vairable JAVA_HOME points to the JDK8 correctly and that java -version shows JDK8 as the installed version

Also make sure you are using the Oracle distribution of Java, rather than something like OpenJDK

After setting up your environment variables I've found you'll also want to close and open a new command prompt.

Also 7.9 is only compatible with 6.3.3 and up.

Sounds like you are in windows. Check to see if there is an unwanted copy of the Java executable in \\Windows\\System32. I had the same issue when I upgraded my local instance.