Recently, I caused a delay in the delivery of a JSF/Spring/Hibernate application running under Tomcat.
The reason was that I built the application with Java 6 and shipped it this way for testing which used Java 5.
Testing identified a major performance problem. Pages that took max. 5 seconds to load were loading in 30 seconds.
It took me a few days before I figured out I was using Java 6 at the time of building.
Now, I am looking at the The JavaTM Virtual Machine Specification and wondering what could have changed between Java 5 and Java 6 if the specification did not change since 1999.