I missed this earlier this week, but here it is anyway. It can be downloaded directly from RIM here.
So, what's cool or new about it? Well, it has an improved IDE and support for new JSRs and such. Some other things from the press release are:
New features of the Java Development Environment for BlackBerry v.4.0 include:
-- An improved Integrated Development Environment (IDE) for enhanced usability and performance
-- An enhanced Application Programming Interface (API) set, documentation and samples that enable developers to tightly integrate their applications with BlackBerry email, text messaging, Web browser and organizer applications. The API enhancements include support for Bluetooth and the BlackBerry "push" architecture.
-- New Java Specification Request (JSR) implementations, including JTWI, MIDP 2.0, CLDC 1.1 and PDAP PIM, that provide developers with a familiar development environment and greater flexibility with applications.
-- A new simulator with improved emulation accuracy, support for new BlackBerry handhelds, and extensive ease-of-use improvements allows developers to quickly emulate and determine how their application will behave on a wide range of BlackBerry devices.
-- Synchronization tools that leverage BlackBerry Enterprise Server for managing data synchronization between back-end applications and handheld applications.
-- XML Generator that allows developers to perform XML-related tasks without having to write additional code.
-- Support for WAP's Push Access Protocol (PAP) providing developers with protocol choice for reliably pushing data with their application.