The name of the Java platform for the enterprise has been simplified. Formerly, the platform was known as Java 2 Platform, Enterprise Edition (J2EE), and specific versions had "dot numbers" such as J2EE 1.4. The "2" has been dropped from the name, as has the minor revision number. So the next version of the Java platform for the enterprise is Java Platform, Enterprise Edition 5 (Java EE 5).
it come from http://java.sun.com/javaee/overview/faq/javaee_faq.jsp#diff