DMGJDK 1.5 vs. JRE 1.4
Good to know: older versions of Java made a point of being backward-compatible. No more. 1.5 bytecode won't run on a 1.4 jre. You can still develop using the latest JDK, though. Just pass the following arguments to your compiler:
-source 1.4 -target 1.4Now, can anyone guess why I was up later than I planned on Monday night? That's right! Because instead of the runtime detecting a version mismatch, it throws a ClassDefNotFoundException, so I spent an hour tearing apart JAR and WAR files to make sure everything was getting included, and double-checking classpath settings and chasing down possible server-related issues. Not sure what made me think of a possible version mismatch, but there you go.