I recently did a peer review of the 7th edition of Core Java for Cay Horstmann and Prentice Hall. When I got my complimentary reviewer's copy in the mail last month, I noticed on the cover that it said "J2SE 5.0". Now of course it should have said "J2SE 1.5" (a.k.a. Tiger) so I thought "oh my gosh! I can't believe they misprinted the version on the cover of the book! how dumb!" But as I started looking through the book and continued to see references to J2SE 5.0, I realized that the joke was probably on me.
So I quickly flexed my Google muscles and searched on "J2SE 5.0 name change" and sure enough, I learned that Sun had changed the name from J2SE 1.5 to J2SE 5.0 "to better reflect the level of maturity, stability, scalability and security built into J2SE" (source).
Yet it's still "Java 2" which "indicates the 2nd generation Java platform, introduced with J2SE 1.2". Does this imply that in the far-flung future we can look forward to "Java 4 version 13"?
Also don't forget that:
Due to significant popularity within the Java developer community, the development kit has reverted back to the name "JDK" from "Java 2 SDK" (or "J2SDK"), and the runtime environment has reverted back to "JRE" from "J2RE". Notice that "JDK" stands for "J2SE Development Kit". The name "Java Development Kit" has not been used since 1.1, prior to the advent of J2EE and J2ME.Got all that?