Where is Java on OS X?

Up to Mountain Lion (10.8) both JDK and JRE were supplied by Apple and installed in

/System/Library/Frameworks/JavaVM.framework/Versions

Since Mavericks (10.9) the JDK is supplied by Oracle and installed in

/Library/Java/JavaVirtualMachines

The JRE is installed through Apple software update in

/Library/Internet Plug-Ins/JavaAppletPlugin.plugin