Anyone can download the source code for a specific version of the Java Development Kit (JDK) and compile its parts for mainstream platforms. The OpenJDK Project includes many distributions, and each one provides a different level of JDK support. In this blog post, we’ll provide a list of some questions to ask to make sure you use the distribution that’s right for you.
What does it mean when we say OpenJDK is an open-source project? Anyone can download the source code for a specific version of the Java Development Kit (JDK) and compile its parts for mainstream platforms. These executables and libraries can be packaged and provided as an OpenJDK distribution, and many different distributions are available. You have your choice of providers — from free and unsupported to commercial providers that offer full support and more.
To claim compatibility with Oracle Java SE, individual binaries within each OpenJDK distribution must pass the Oracle-owned Technology Compatability Kit (TCK) suite of tests associated with that version of Java. Because there are many TCK-compliant OpenJDK providers, evaluating them can be challenging. Some considerations between the different providers can include:
Which Java versions are supported?
As of January 2025, there are four Long-Term Support (LTS) versions of Java among more than 20 in total. It’s easy to find JDK support for the most current LTS release, Java 21, but the further back you go, the fewer providers there are to support older versions. Oracle ended free support for the previous LTS version, Java 17, in October 2024. Only Azul supports Java 6 and Java 7.
Which platforms are supported?
Most users run applications on mainstream operating systems like Linux and Windows and use common processors like those from Intel and AMD. If your environment includes less-common platforms like ARM-based processors, or perhaps you still run Java applications on the Solaris operating system, you should know whether the distribution provides builds for them and whether it continues to provide fixes?
How long will a version be supported?
Even among LTS versions, different distributions may offer various maintenance and support lengths. If your plans are to keep the current versions running for 10 years before making any changes to the code, you’ll want to make sure that you have LTS for that version for at least a decade. Some distributions may also commit to supporting a version after they stop providing the scheduled updates. In this passive support phase, users can still report issues and, if necessary, the build provider may provide a special update containing a fix.
See the Azul Support Lifecycle Roadmap
How quickly are updates available?
The scheduled JDK updates are developed through the OpenJDK project and embargoed by the OpenJDK Vulnerability Group until a preplanned date and time. Before investing in an OpenJDK distribution, you should know its track record for providing updates within hours of the embargo lifting and whether it has had long delays in the past. Ask if it has an SLA specifying when an update is guaranteed to be available. Update speed is important because, after the embargo is lifted, details of security vulnerabilities are made public, starting a race against time. Bad guys start developing exploits; and if your updates are unavailable for days or even weeks, your systems are at risk.
Are stabilized updates available?
Oracle Java SE provides two formats for each update
- Critical Patch Update (CPU): a stabilized security update
- Patch Set Update (PSU): the full update
To maintain the maximum level of JDK support, both are essential. When Oracle releases a patch for a known vulnerability, your organization can quickly implement a CPU to patch the vulnerability. If all you have is a PSU, you have to implement the entire update, which is time-consuming, resource-intensive, and requires regression testing. Only Oracle and Azul provide CPUs.
Even with TCK compliance, some Java users still feel uncomfortable with anything but Oracle Java support, which is expensive. Azul Platform Core customers typically save 70% versus Oracle Java SE.
Platform Core
Get to know Azul’s product based on OpenJDK.
