[carlo@palantir tmp]$ /opt/oracle/jdk1.8.0/bin/javac -target 1.8 HelloWorld.java
[carlo@palantir tmp]$ /opt/oracle/jdk1.7.0/bin/java HelloWorld
Exception in thread "main" java.lang.UnsupportedClassVersionError: HelloWorld : Unsupported major.minor version 52.0
Crock... :-)