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Oracle® JRockit Introduction
Release R28

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1 About the Oracle JRockit JDK

Oracle JRockit provides tools, utilities, and a complete run-time environment for developing and running Java applications. JRockit JDK includes the Oracle JRockit JVM, which is developed and optimized for Intel architectures to ensure reliability, scalability, and manageability for Java applications.

This chapter contains information about the following topics:

1.1 What Is the JRockit JVM?

The JRockit JVM is a high-performance JVM developed to ensure reliability, scalability, manageability, and flexibility for Java applications. The JRockit JVM provides improved performance for Java applications deployed on Intel 32-bit (Xeon) and 64-bit (Xeon and SPARC) architectures at significantly lower costs to the enterprise. Further, it is the only enterprise-class JVM optimized for Intel architectures, providing seamless interoperability across multiple hardware and operating system configurations. The JRockit JVM enables your Java applications to run optimally on Windows and Linux operating systems (both 32-bit and 64-bit architectures). The JRockit JVM is especially well-suited for running Oracle WebLogic Server.

For more information about JVMs, see The Java Virtual Machine Specification at:

About the Oracle JRockit JDK

The JRockit JVM is one component of the JRockit JDK JDK. In addition to the JRockit JVM, the JDK contains the Java Run-time Environment (JRE). The JRE contains the Java class libraries (as specified by the Java Platform, Standard Edition 6 API Specification) and a set of development tools, such as a compiler.

For more information about the contents of the JRockit JDK, see Section 1.6, "Contents of a JRockit JDK Installation".

1.2 JRockit JDK Release Numbering Scheme

Every JRockit JVM release comes with several Java versions. For example, JRockit JVM R28.0 comes with Java SE versions 5.0 and 6. A Java version can be compatible with multiple JRockit JVM releases.

The JRockit JDK release number consists of the following elements:

For example, Oracle JRockit JDK 6 R28.0.0 indicates the 28.0.0 release of JRockit JVM used with Java SE 6; similarly, Oracle JRockit JDK 5.0 R28.0.0 indicates the 28.0.0 release of the JRockit JVM used with J2SE 5.0.

The following is an example of a complete release number:


In this example, R28.0.0 is the JRockit JVM release, 1.6.0_01 is the Java version, and windows-ia32 is the platform on which the release runs.

1.3 Supported Configurations for the Oracle JRockit JDK

Oracle JRockit JDK is compatible with J2SE 5.0 and Java SE 6.

For a full list of processor types and operating systems that JRockit JDK supports, see Oracle JRockit JDK Supported Configurations at

1.4 Support and Error Correction Policies

The Oracle Lifetime Support Policy for Oracle Fusion Middleware is available at

The Software Error Correction Policy is available in Support Note ID 950131.1.

1.5 Compatibility Between JRockit JDK and HotSpot

Java APIs

All Java APIs follow the Java compatibility statement (

Proprietary JRockit JVM APIs

Command Line Options

1.6 Contents of a JRockit JDK Installation

The JRockit JDK is similar, in the file layout, to the HotSpot JDK, except that the JRockit JDK includes a new JRE with the JRockit JVM. All of the class libraries have the same behavior in the JRockit JDK as in the HotSpot JDK.

Table 1-1 describes the contents of the directories in a JRockit JDK installation.

Table 1-1 Contents of a JRockit JDK Installation

Directory Contents


The bin directory contains development tools and utilities to help you develop, execute, debug, and document programs written in the Java programming language.

The JRockit JDK includes the standard tools distributed with the typical Java JDKs. Most of these tools work well with Java development projects, but you can use any other third-party tools, compilers, debuggers, IDEs, and so on that work best in your situation.

The tools included with the JRockit JDK are:

  • the javac compiler

  • the jdb debugger

  • javadoc, which is used to create documentation in HTML format for the JVM API

For more information about these tools, see the documentation at


The demo directory contains demos on using the libraries included in the JRockit JDK installation.


The include directory contains header files that support native-code programming using the Java Native Interface (JNI) and the Java Virtual Machine Tools Interface (JVMTI), and other functionality of the Java SE Platform.


The jre directory contains the JRockit JVM implementation of the Java run-time environment. The run-time environment includes the JRockit JVM, class libraries, and other files that support running Java programs.

Java Virtual Machine: By definition, the JVM is the JRockit JVM, as described in this documentation.

Standard Java SE JRE Features: In addition to JRE components specific to the JRockit JDK, the JRE also contains components found in the HotSpot implementation of the JRE. For a complete list of the standard Java SE JRE features, see the following documentation:

Note about JRE class files: The JRE class files distributed with the JRockit JDK are the same as those in the HotSpot JDK, except for a small number of files that are tightly coupled to the JVM and are, therefore, overridden in the JRockit JDK. No classes are omitted.


The lib directory contains additional class libraries and support files required by the development tools.


The sample directory contains the source files for a simple NIO-based HTTP/HTTPS Server written in Java. The server was written to demonstrate some features of the Java 2 platform. The demo is not meant to be a full tutorial, and it is assumed that you have some familiarity with the subject.

1.7 JRockit JVM Command-Line Options

The JRockit JVM configuration and tuning parameters are set by using specific command-line options, which you can enter either along with the start-up command or include in a start-up script.

For more information, see the Oracle JRockit Command-Line Reference.