If you go to compile mojarra, the JSF reference implementation, and get this error: javac: invalid target release: 1.8 Do not worry.
It just means that you are trying to compile mojarra with an older version of java. Mojarra requires java 1.8 at least as of this blog post.
Just change your JAVA_HOME to point to a java 1.8+ version and try again.
Hope that helps.