Generally if you are not sure where your JAVA_HOME is the first thing you would do is type in the following command
But more times than usual if you have not intentionally set this variable in your MAC you would see an empty response. So now how would you proceed to find the real JAVA_HOME. Some times a quick solution is looking in /System/Library/Frameworks/JavaVM.framework/Versions. Still there can be a lot of Java HOME's in there (like what happened to me).