OpenJDK versus Oracle JDK

Java is everywhere. First released by Sun Microsystems and later acquired by Oracle, Java is a programming language and computing platform created to run anywhere. 

The Java Platform, Standard Edition Development Kit (JDK) is a development environment for building applications using the Java programming language that  includes tools useful for developing and testing programs written in the Java programming language and running on the Java platform.

The Red Hat® build of OpenJDK is a free and open source implementation of the Java Platform, Standard Edition (Java SE), as a result of a 2006 initiative by Sun Microsystems to open source their Java implementation under the OpenJDK project. It is an alternative that allows organizations to stabilize and standardize their Java environments for years to come with little to no transition effort or traditional licensing hassles. 

Oracle JDK and OpenJDK are each a set of software and specifications known as Java Development Kits.  From Java 11 onward, Oracle JDK and OpenJDK are the same in build with the inclusion of features like Flight Recorder andMission Control. Essentially, there are little to no code changes between Oracle JDK and OpenJDK, so they are functionally very similar. 

The biggest difference between OpenJDK and Oracle JDK is that OpenJDK is an open source project that is maintained by Oracle, Red Hat, and the community, whereas Oracle JDK is closed source, requires a paid license, and is maintained by Oracle. With that difference, there are a few features that aren’t available with OpenJDK due to the features being closed source or restricted by licensing.

Because OpenJDK is an open source development kit, this does result in support and cost differences from Oracle JDK. OpenJDK serves as an accessible open source alternative to Oracle JDK for reasons including:

• Cost: For those needing enterprise support: Red Hat’s build of OpenJDK is included at no additional cost with Red Hat Enterprise Linux® (RHEL), Red Hat OpenShift®, and Red Hat Application Services subscriptions.
• Consolidate: You can consolidate Java support for the cloud (application server or runtime, JDK, Kubernetes) by standardizing on OpenJDK.

As part of a cloud-native modernization process, OpenJDK offers continuous development, performance improvements, security updates, and deployment flexibility, making it ideal for  running on application servers, in containers or on Kubernetes.

Between OpenJDK and Oracle JDK, there are no differences in how both JDKs perform with Java SE specification compliant code. Considering the few feature differences, it is up to you to decide which offers more advantages and move forward with the migration.

From cost to Java support need, there are many factors to consider when considering which JDK to choose. Many Java experts encourage users to migrate to OpenJDK as soon as possible, noting that a healthy migration strategy should start with a thorough inventory and risk analysis. Large organizations may also need to assess their needs for support and stability. 

Something else to consider is whether your stack is Linux based. If it is, migrating to OpenJDK can be beneficial because OpenJDK is the default Java distribution for Linux Ubuntu, Fedora, RHEL, and OpenSUSE distributions.

One caution when evaluating the JDKs: if you are migrating from an older version of OracleJDK, such as Java 8, if an application made use of internal and unspecified APIs, they may not be part of the OpenJDK code base.

Plus, with the newest pricing changes by Oracle, you and your organizations may explore a change to OpenJDK. 

What can you do to modernize the JDK of your Java applications?

Red Hat and its range of system integration partners have the expertise to facilitate a successful migration to OpenJDK. The recommended approach follows five steps.

Recommended approach:

1. Create an inventory of applications and JVMs/versions: Understand existing usage, Oracle licensing, versions, security issues, dependencies, and grouping
2. Analyze applications for potential code changes or risk: Identify in an initial migration plan any areas that represent risk or require change
3. Prepare operational handling (deployment and updates): Get ready operational processes to deploy and manage your JDK
4. Run pilot migration with a set of applications: Run a representative set of apps has run through the process (changes if any, testing, deployment) and form an updated migration plan
5. Migrate at scale in iterations: Use the OpenJDK migration factory

As the second largest JDK contributor next to Oracle, Red Hat can help you and your organization build, manage, and scale your applications with the support and services you need. 

Red Hat holds the stewardship role of OpenJDK 8u and 11u versions, and with little to no code changes, Java compliance, and multi-platform support, OpenJDK can be your best alternative. 

The Red Hat build of OpenJDK is included as a fully supported offering in RHEL, OpenShift, and Middleware subscriptions at no extra cost. Additionally, Red Hat’s application platform, including RHEL, OpenShift, Application Services, and Ansible, provides the ideal JDK for a hybrid-cloud architecture. Red Hat has also expanded support for Java applications by including support for Eclipse Temurin.

Lastly, Red Hat’s migration toolkit for applications can help you assess, prioritize, and modernize your applications at scale to use Red Hat OpenShift. Beyond helping with JDK migrations it can help you analyze and modernize your Java applications as a whole.