Apple has released Macintosh Runtime for Java 2.1, which offers substantial performance improvements over previous versions of MRJ and can be used with Microsoft's Internet Explorer Web browser. (Microsoft dropped support for their own Java virtual machine immediately after Sun won a preliminary injunction against Microsoft's Java implementations; see TidBITS 456.) MRJ 2.1 complies with Sun's Java JDK 1.1.6 specification, optionally supports Sun's Java Foundation Classes and Swing interface toolkit (versions 1.0.3 and 1.1), and adds support for AppleScript (although we don't know how useful this will be in the short term). Although MRJ 2.1 still doesn't run every Java applet under the sun (in fact, the release notes warn users away from Yahoo Games while Apple investigates problems), MRJ 2.1 works with Internet Explorer - just make sure MRJ is selected as Explorer's Java virtual machine - and Java development environments for the Macintosh. Netscape browsers use their own Java implementation and can't currently use MRJ.

MRJ 2.1 requires a PowerPC-based Mac running Mac OS 7.6.1 or later (Mac OS 8.1 or later recommended) with at least 24 MB of RAM, 20 MB of free disk space, and Open Transport 1.1 or better. MRJ 2.1 installs Text Encoding Converter 1.4.2 on all systems, and if you're using Mac OS 7.6.1, it installs version 1.0.3 of the Appearance control panel. Note that MRJ 2.1 does not ship with the Apple Applet Runner; you can use Apple's Applet Runner 2.0 (which shipped with MRJ 2.0, and hence with Mac OS 8.1 and higher) or download it with the MRJ SDK from Apple's developer Web site. MRJ 2.1 is a 7.8 MB download from Apple's FTP site; Apple hasn't updated its MRJ Web pages as of this writing.