Mac OS Runtime for Java (MRJ, originally Macintosh Runtime for Java) was Apple's proprietary

virtual machine In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...

for Java-based applications in the

classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...

(i.e. versions prior to

Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...

). Both a runtime environment and a

software development kit A software development kit (SDK) is a collection of software development tools in one installable package. They facilitate the creation of applications by having a compiler, debugger and sometimes a software framework. They are normally specific to ...

(SDK) are available. The runtime environment includes a

JIT compiler In computing, just-in-time (JIT) compilation (also dynamic translation or run-time compilations) is a way of executing computer code that involves compilation during execution of a program (at run time) rather than before execution. This may cons ...

developed by

Symantec Symantec may refer to: *An American consumer software company now known as Gen Digital Inc. *A brand of enterprise security software purchased by Broadcom Inc. Broadcom Inc. is an American designer, developer, manufacturer and global supplier ...

, the standard Java class library from Sun, additional classes providing Macintosh-specific functionality, and the Apple Applet Runner (a lightweight application for running Java applets without the overhead of a

web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on ...

). A number of web browsers could use MRJ to run Java applets in web pages, including

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical user interface, graphical web browsers developed by Microsoft which was used in the Microsoft Wind ...

iCab iCab is a web browser for Mac OS by Alexander Clauss, derived from Crystal Atari Browser (CAB) for Atari TOS compatible computers. It was one of the few browsers still updated for the classic Mac OS prior to that version being discontinued afte ...

and

HotJava HotJava (later called HotJava Browser to distinguish it from HotJava Views) was a modular, extensible web browser from Sun Microsystems implemented in Java. It was the first browser to support Java applets, and was Sun's demonstration platform ...

. The SDK includes ports of most of the tools from Sun's Java Development Kit (in the form of MPW 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. MRJ v2.2.5 was compatible with Sun's Java Development Kit version 1.1.8. Since the transition to Mac OS X, Apple has discontinued MRJ and instead maintains and distributes a port of Oracle's

HotSpot Hotspot, Hot Spot or Hot spot may refer to: Places * Hot Spot, Kentucky, a community in the United States Arts, entertainment, and media Fictional entities * Hot Spot (comics), a name for the DC Comics character Isaiah Crockett * Hot Spot (Tra ...

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.

Implementations

* Java 1.0.2 with Mac OS Runtime for Java v 1.5.

(starting with version 1.5, MRJ included a JIT compiler) * Java 1.1.8 with Mac OS Runtime for Java v 2.2.

References

External links

* Discontinued Java virtual machines Classic Mac OS {{Apple-stub