J9 Virtual Machine (JVM)

The IBM® J9 virtual machine (JVM) is the platform-specific component that runs a Java™ program.

At run time, the JVM interprets the Java bytecode that has been compiled by the Java Compiler. The JVM acts as a translator between the language and the underlying operating system and hardware. A Java program requires a specific JVM to run on a particular platform, such as Linux, z/OS®, or Windows.

The main components of the IBM VM are:
  • JVM Application Programming Interface (API)
  • Diagnostic component
  • Memory management
  • Class loader
  • Interpreter
  • Platform port layer

For further information about the JVM, see Components of the IBM Virtual Machine for Java.

Different versions of the IBM SDK contain different implementations of the JVM. You can identify the implementation in the output from the java -version command, which gives these strings for the different implementations:
Implementation Output
7
IBM J9 VM (build 2.6, JRE 1.7.0 ...
6
IBM J9 VM (build 2.4, JRE 1.6.0 IBM...