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Mac OS Runtime for Java
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<p>Mac OS Runtime for Java (MRJ, originally Macintosh Runtime for Java) was <a href="/facts/Apple_Inc./oTJYta3k">Apple's</a> proprietary <a href="/facts/Java_virtual_machine/l9Nzrsun">virtual machine</a> for <a href="/facts/Java_(programming_language)/9ScgFyAL">Java-based</a> applications in the <a href="/facts/Classic_Mac_OS/I5fQq44K">classic Mac OS</a> (i.e. versions prior to <a href="/facts/Mac_OS_X/Y93vVpTm">Mac OS X</a>). Both a runtime environment and a <a href="/facts/Software_development_kit/2Hkk6Hbs">software development kit</a> (SDK) are available. </p><p>The runtime environment includes a <a href="/facts/Just-in-time_compilation/rEYDsd8l">JIT compiler</a> developed by <a href="/facts/NortonLifeLock/uWvBqako">Symantec</a>, the standard Java <a href="/facts/Class_library/xRzL3P7q">class library</a> from <a href="/facts/Sun_Microsystems/VJ9EzEFd">Sun</a>, additional classes providing Macintosh-specific functionality, and the Apple Applet Runner (a lightweight application for running Java <a href="/facts/Applet/XDSonw6C">applets</a> without the overhead of a <a href="/facts/Web_browser/2pfyymLs">web browser</a>). A number of web browsers could use MRJ to run Java applets in web pages, including <a href="/facts/Microsoft/nGIDDXdx">Microsoft</a> <a href="/facts/Internet_Explorer/uL8a4Y5l">Internet Explorer</a>, <a href="/facts/ICab/1pLeNcaT">iCab</a> and <a href="/facts/HotJava/47DkRuQB">HotJava</a>. </p><p>The SDK includes <a href="/facts/Porting/7s6tFs8B">ports</a> of most of the tools from Sun's <a href="/facts/Java_Development_Kit/qL5cDos6">Java Development Kit</a> (in the form of <a href="/facts/Macintosh_Programmer%27s_Workshop/W36b0FMc">MPW</a> tools and Macintosh applications), additional tools for packaging Java applications as double-clickable Macintosh applications, libraries for Macintosh-specific functionality, and documentation for the MRJ-specific classes and tools. </p><p>MRJ v2.2.5 was compatible with Sun's Java Development Kit version 1.1.8. </p><p>Since the transition to Mac OS X, Apple has discontinued MRJ and instead maintains and distributes a port of <a href="/facts/Oracle_Corporation/0z14FygH">Oracle's</a> <a href="/facts/HotSpot_(virtual_machine)/m6vjRXvm">HotSpot</a> Java virtual machine. As of Java 7, Apple has discontinued its own JRE, and Java support on OS X/macOS now comes directly from Oracle. </p>