OpenJDK vs Oracle JDK

Solution Verified - Updated

Environment

  • OpenJDK
  • OracleJDK

Issue

  • Any differences between the Red Hat OpenJDK and the Oracle JDK?
  • Any factors to consider when migrating from Oracle JDK to OpenJDK?

Resolution

Following is a basic list and not specific to any java version.

  • Font: The font library is different. This means slightly different text layout in some cases. Oracle JDK 8 is distributed with a font, while OpenJDK 8 relies on at least one font being available in the system. Neither OpenJDK 11+ or Oracle JDK 11+ have fonts embedded.

  • CMS: Same for the colour management system. OpenJDK uses the same solutions as the rest of RHEL (FreeType & LCMS) while the proprietary JDK has established existing code that it has used for many years.

  • OpenJDK can use the RHEL system NSS crypto library, instead of the JDK's built-in one. This mostly affects elliptic curve cryptography, where OpenJDK supports all of the RHEL curves and none of the others.

  • 2D library: OpenJDK has its own 2D library, different from the proprietary JDK. This means that its performance may differ.

  • Application Class Data Sharing is part of OpenJDK since OpenJDK 10. This feature reduces the memory footprint by sharing class metadata.

  • OpenJDK doesn't support the Resource Management API for Java.

  • OpenJDK doesn't support the Simple Network Management Protocol API.

  • OpenJDK has its own browser plugin and Java Web Start application (icedtea-web package), written independently of Oracle. Icedtea-web is currently supported on RHEL with OpenJDK 7 and OpenJDK 8 and on Windows with OpenJDK 8. However, following Oracle's path, IcedTea-Web is being deprecated on OpenJDK 11.

  • OpenJDK doesn't support Cooperative Memory Management. This allows the user to tune the G1 garbage collector depending on a compromise between memory usage and performance. Cooperative Memory Management was deprecated for removal with no replacement in JDK10 and removed in JDK11.

  • OpenJDK supports system-tap.

  • OpenJDK is provided with full-debug clone-build (-debug- subpackages).

  • OpenJDK comes with javadocs. Both zipped and uncompressed.

  • OpenJDK is delivered with full sources.

  • OpenJDK uses system tzdata and system certificates (Oracle has these bundled).

  • OpenJDK 8 and 11 from Red Hat fully support Shenandoah, a low pausetime Garbage Collector for large heaps.

  • OpenJDK Jave Flight Recorder (JFR) is a different internal implementation than Oracle JDK in 8u, and was backported from the implementation available in OpenJDK 11; furthermore, it is only available starting from OpenJDK 8u262. The implementation of JFR is missing in OpenJDK 9 and 10. Since 11 both OpenJDK and Oracle JDK have the same implementation.

  • The Red Hat build of OpenJDK8 32-bit build for RHEL7 does not include the client VM.

  • The com.sun.image.codec.jpeg package is not included in OpenJDK because it has a 3rd party license that prevents open-sourcing it.

  • The Red Hat build of OpenJDK distribution does not include JavaFX/OpenJFX.

  • JDK8 minor release numbers are different. The OpenJDK minor release number is 1 more than Oracle. For example, the January 2025 JDK8 quarterly release is update 442 for OpenJDK and update 441 for Oracle.

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