(...) the submission that you return must have been tested and shown to work under a production (not development) version of the Sun Microsystems' Java 2 plataform and that plataform must not have been superseded by a new production version for more than 18 months by the time you make your submission.
You may use the link in the next question and do the math. When in doubt, just use the latest version.
Example calc: 1.5.0 was released on Sept 29, 2004, superseding 1.4.2. However you can still use 1.4.2 until it has been superseded by 18 months, so adding the 18 months to Sept 29, 2004 means that you can still use 1.4.2 until March 29, 2006.
From April 2006 you must use at least JDK 1.5. You can no longer use 1.4.2 or prior versions.