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The Custom edition JREs are suitable for embedded systems that need to run 'desktop-level' Java applications. Each CJRE is compatible with Sun's Java 5 platform, which means that it executes the J2SE 5 compatible Java applications on the target device and can supports the customer-requested Java 5 features (e.g. assertions).  CJREs compatible with Sun's Java SE 6 platform will be available in near future.

Each CJRE includes the target-specific ports of:
  • IBM's J9 Virtual Machine (J9VM) compatible with Sun's latest Java ME CDC VM 1.1.2 defined by JSR-218.
  • IBM's Just-in-Time (JIT) compiler integrated with the port of J9VM.
  • Harmony Class Library (HCL) from Apache.org.
  • A "glue layer" of Java classes and C/C++ native methods that make each port of Harmony work seamlessly and effectively with the corresponding port of J9VM.
HCL is highly compatible with Sun's Java 5 (J2SE 1.5) platform1 and also includes most of the functionality that is optionally available for MJREs, such as the database connectivity (JDBC), remote method invocation (RMI), crypto and other packages.  In addition, HCL can optionally support:
  • Java SE AWT/Swing/Java2D graphics adapted to work effectively with the following native libraries:
    • X or DirectFB libraries on Linux-based targets
    • GDI on Windows CE/Mobile-based targets
  • Serial/Parallel port communication using IBM's JavaComm library.
Each CJRE can include the customer-requested target-specific ports of the following client-side runtimes:
Each CJRE can include the target-specific ports of the following application-level packages:
  1. J2SE 1.5 compatibility involves support from both Class Library and Virtual Machine.  J9 VM provides support for some (but not all) of the required functionality, e.g. assertions are accepted, but not acted upon.  Additional supporting VM functionality can be added based on customer needs.