OpenJDK Demystified: Navigating the Java Landscape

What is OpenJDK?

  • OpenJDK is an open-source implementation of the Java Platform, Standard Edition.
  • Offers a development environment for building Java applications.
  • Includes the Java Runtime Environment (JRE), compilers, and libraries.
  • It’s the official reference implementation for Java SE.
  • Licensed under the GNU General Public License v2.
  • Supported by a community of developers.

Introduction to OpenJDK


OpenJDK, the Open Java Development Kit, is a pivotal element in Java programming, yet its comprehensive understanding often eludes many developers.

Here, we aim to demystify OpenJDK, offering a clear, informative, and unbiased exploration of its capabilities and features.

Key Aspects of OpenJDK

  • What is OpenJDK? OpenJDK is an open-source implementation of the Java Platform, Standard Edition. It provides a free and accessible development environment for building Java applications.
  • Origin and Evolution: Initiated by Sun Microsystems in 2006, OpenJDK represented a significant step towards open-source in the Java ecosystem, promoting transparency and community-driven development.
  • Current Relevance: Today, OpenJDK is the backbone of numerous Java applications, reflecting its critical role in contemporary software development.

Definition and Basic Understanding of OpenJDK

OpenJDK offers a comprehensive toolkit for Java developers, encompassing the necessary components to develop, debug, and run Java applications.

It includes the Java Runtime Environment (JRE), compilers, and libraries, ensuring a robust framework for Java development.

OpenJDK’s prominence in the developer community stems from its accessibility and open-source nature, which encourages innovation and collaboration.

OpenJDK’s Development History

  • 2006: Sun Microsystems announces the release of OpenJDK, fundamentally changing the landscape of Java development.
  • Subsequent Developments: Over the years, OpenJDK has evolved, incorporating enhancements and updates that keep pace with the ever-changing demands of software development.
  • Community Involvement: A significant aspect of OpenJDK’s success is the active participation of a global community of developers, continually contributing to its improvement and refinement.

Comparison with Oracle JDK: A Detailed Analysis

Comparison with Oracle JDK

Critical Differences Between OpenJDK and Oracle JDK

  1. Licensing:
    • OpenJDK is licensed under the GNU General Public License v2 with a linking exception. This licensing model means that while the software is free and open-source, modifications and redistributions are also free, provided the derived work remains open-source.
    • Oracle JDK: Traditionally, Oracle JDK was licensed under the Oracle Binary Code License Agreement, which was more restrictive. However, since Oracle JDK 11, it has been offered under a dual-license model: a free OpenJDK/GPL license and a paid commercial license for extended support and additional features.
  2. Release Schedule:
    • OpenJDK: Adheres to a more rapid release cycle. OpenJDK versions are typically released every six months, aligning with the faster evolution of Java features.
    • Oracle JDK: Oracle JDK follows a similar release pattern as OpenJDK for its open-source releases. However, Oracle offers long-term support (LTS) versions under its commercial license, which receive updates and support for a more extended period.
  3. Performance Aspects:
    • OpenJDK and Oracle JDK: There is a common misconception that Oracle JDK performs better than OpenJDK. In reality, the performance of both JDKs is quite similar. Oracle JDK and OpenJDK are built from the same codebase. However, Oracle JDK might include additional proprietary optimizations, especially in areas like garbage collection and JVM heuristics, which can make a difference in specific scenarios.
  4. Additional Features:
    • Oracle JDK: The commercial version of Oracle JDK may include additional features and tools unavailable in OpenJDK. These features often focus on enterprise needs, such as advanced monitoring, management, and deployment capabilities.
    • OpenJDK: While OpenJDK might not have all the proprietary features of Oracle JDK, it is often the first to receive new Java features due to its rapid release cycle.

Significance of OpenJDK Being the Official Reference Implementation

  1. Reference for Java SE:
    • From Java SE 7, OpenJDK has been the official reference implementation for the Java Platform, Standard Edition. This status means the Java SE specification is defined based on what is implemented in OpenJDK.
    • This role reinforces OpenJDK’s importance in the Java ecosystem, as changes and updates in OpenJDK directly influence the direction of Java SE.
  2. Impact on Java Development:
    • OpenJDK’s position as the reference implementation makes it a crucial platform for testing new Java features. It serves as the Java community’s primary platform for innovation and experimentation.
    • Developers and organizations often choose OpenJDK for its cutting-edge features and active community support. The open-source nature of OpenJDK encourages community contributions and transparency in the development process.
  3. Influence on Other JDK Distributions:
    • Many other Java distributions, including vendor-specific JDKs, are based on or derived from OpenJDK. This influence underscores the significance of OpenJDK in shaping the broader Java landscape.

Evolution of Java and OpenJDK

Chronological Overview of Java Versions and OpenJDK Projects

Here’s a chronological overview of Java versions and OpenJDK projects:

Java Versions

  1. Java 1.0 (1996): The first public implementation. Introduced the “Write Once, Run Anywhere” philosophy.
  2. Java 1.1 (1997): Added inner classes and JavaBeans.
  3. Java 2 (J2SE 1.2) (1998): This version was a major revision; it introduced the Swing graphical API and the concept of the Java Collections Framework.
  4. J2SE 1.3 (2000): Introduced HotSpot JVM, significantly improving performance.
  5. J2SE 1.4 (2002): Introduced the assert keyword, regular expressions, non-blocking IO (NIO), and logging API.
  6. Java SE 5.0 (2004): Marked a significant language evolution with features like generics, annotations, autoboxing, and the enhanced for loop.
  7. Java SE 6 (2006): Focused on performance improvements and introduced features like Scripting Language Support (support for JavaScript and other languages).
  8. Java SE 7 (2011): Introduced the try-with-resources statement, the Fork/Join Framework, and the new FileSystem API.
  9. Java SE 8 (2014): A milestone release introducing lambda expressions, streams API, and the new Date and Time API.
  10. Java SE 9 (2017): Introduced the module system (Project Jigsaw) and other enhancements like the JShell tool.
  11. Java SE 10 (2018): Introduced local variable type inference (var keyword) and other smaller enhancements.
  12. Java SE 11 (2018): Made notable changes, including the removal of Java EE modules, the introduction of the HttpClient API, and more.
  13. Java SE 12 to 19 (2019-2023): These versions focused on incremental improvements and optimizations, including new features like switch expressions, text blocks, pattern matching, for instance, and records.

OpenJDK Projects

OpenJDK (Open Java Development Kit) is the free, open-source implementation of the Java Platform, Standard Edition.

  1. OpenJDK 6 (2006): The first version released under the GNU General Public License (GPL).
  2. OpenJDK 7 (2011): Corresponded with Java SE 7.
  3. OpenJDK 8 (2014): Corresponded with Java SE 8 and is widely used in many applications.
  4. OpenJDK 9 to 19 (2017-2023): These versions align with the respective Java SE versions, focusing on enhancements and optimizations in the Java platform.

Evolution Highlights

  • Performance Improvements: Each version of Java and OpenJDK has brought performance enhancements, better garbage collection, and optimizations in the JVM.
  • Language Features: Over the years, Java has introduced significant language features like lambda expressions, modules, and pattern matching, making the language more expressive and efficient.
  • Standardization and Open Source: The shift to OpenJDK marked a significant step towards open-source collaboration and standardization in Java development.
  • Release Cadence Change: Post Java 9, Oracle introduced a new release cadence with a new version every six months, focusing on incremental improvements and quicker adoption of new features.
  • Long-term Support (LTS) Versions: Not all versions are LTS; currently, Java 8, 11, and 17 are considered LTS versions, offering long-term support for enterprises.

Java’s evolution reflects its adaptability and commitment to meeting the modern developer’s needs while maintaining a stable and reliable platform for application development.

OpenJDK in Practice

Implementation and Use in Real-World Scenarios

OpenJDK is not just a development kit in theory; its practical application is vast and varied:

  • Enterprise Applications: OpenJDK forms the backbone of many enterprise-level Java applications, offering a stable and secure platform.
  • Cloud-Based Solutions: With the rise of cloud computing, OpenJDK has adapted to meet cloud-based application development needs, providing the necessary tools and libraries.
  • Mobile and IoT Devices: OpenJDK also finds its use in mobile and IoT device programming, thanks to its cross-platform nature.

Explanation of OpenJDK Projects and Their Significance

  • Project Diversity: OpenJDK encompasses a variety of projects, each focusing on different aspects of Java development, like Project Amber for language productivity features and Project Loom for concurrency.
  • Community Contributions: These projects are driven by community contributions, ensuring Java stays relevant and innovative.

The Role of OpenJDK in Various Operating Systems and Platforms

  • Cross-Platform Compatibility: One of OpenJDK’s key strengths is its cross-platform compatibility, making it a preferred choice for developers across different operating systems.
  • Integration with Operating Systems: OpenJDK seamlessly integrates with various operating systems, including major ones like Linux, Windows, and macOS, ensuring a uniform development experience.
  • Support for Diverse Platforms: Beyond traditional desktop and server environments, OpenJDK’s adaptability extends to newer platforms, including cloud infrastructure and mobile devices.

Best Practices and Recommendations

Best Practices and Recommendations

Guidelines for Using OpenJDK in Development Projects

  • Stay Updated: Regularly update the latest OpenJDK version to leverage new features and security fixes.
  • Environment Compatibility: Ensure compatibility of your development environment with the OpenJDK version you’re using, including IDEs and build tools.
  • Performance Tuning: Optimize JVM settings to suit your application’s needs for better performance.
  • Security Practices: Regularly scan and update OpenJDK to patch any security vulnerabilities.
  • Community Engagement: Participate in OpenJDK community forums and discussions for insights and support.

Advantages of Choosing OpenJDK

  • Cost-Effectiveness: Being open-source, OpenJDK is free, reducing software licensing costs.
  • Robust Community Support: Benefit from a vast developer community’s collective wisdom and contributions.
  • Flexibility and Customization: Adapt and customize OpenJDK to fit specific project requirements.
  • Cross-Platform Compatibility: Develop applications that run seamlessly across different platforms.
  • Regular Updates: Frequent updates mean access to the latest features and improvements.

Release Cycle and Versioning

  1. Release Cadence:
    • OpenJDK follows a predictable release cycle, with a new major release every six months. This cadence allows for a more rapid introduction of new features, enhancements, and bug fixes.
    • Each release is numbered based on a feature release versioning system, for example, OpenJDK 11, 12, etc.
  2. Long-Term Support (LTS) Versions:
    • Specific versions of OpenJDK are designated as Long-Term Support (LTS) releases. These versions receive updates and support for an extended period, typically several years.
    • LTS versions are chosen every few years (e.g., OpenJDK 8 and OpenJDK 11 are current LTS versions as of my last update). The selection of LTS versions is usually based on the significance and stability of the release.

Update and Patching Process

  1. Regular Updates:
    • OpenJDK versions receive regular updates, which include security fixes, performance enhancements, and bug fixes. These updates are essential for maintaining the security and efficiency of Java applications.
    • Updates are typically made available every six months during the new feature release.
  2. Backporting to LTS Versions:
    • Critical updates, especially security patches, are often backported to LTS versions. This means that even after a new version is released, LTS versions receive essential updates.
    • The backporting process is crucial for organizations that cannot frequently update to the latest version of Java due to compatibility or policy reasons.

Community Support and Contributions

  1. Open Source Community:
    • OpenJDK is an open-source project maintained and supported by a vibrant community of contributors, including individual developers, organizations, and enterprises.
    • This community-driven approach ensures diverse perspectives and expertise in addressing issues and developing new features.
  2. Contribution Process:
    • Developers and organizations can contribute to OpenJDK by submitting bug fixes, enhancements, and new feature proposals. The contribution process typically involves discussions with the community, review by maintainers, and adherence to OpenJDK’s coding standards and guidelines.
  3. Issue Tracking and Resolution:
    • Issues and bugs are tracked through public issue-tracking systems. This transparent approach allows anyone to report issues, track progress, and review resolutions.
    • The community actively participates in triaging, diagnosing, and resolving issues, ensuring continuous improvement of the platform.

Vendor-Specific Support Options

  1. Third-Party JDK Distributions:
    • Several organizations offer their distributions of OpenJDK, providing additional support and features. Examples include AdoptOpenJDK, Amazon Corretto, Red Hat’s build of OpenJDK, and others.
    • These distributions often provide additional support options, including extended updates for older versions, performance enhancements, and enterprise-focused features.
  2. Commercial Support:
    • Commercial support options are available from various vendors for organizations requiring more extensive support. This support may include guaranteed response times, dedicated support teams, and extended lifecycle support for specific versions.


1. Is OpenJDK as stable as Oracle JDK?

Answer: OpenJDK is generally considered as stable as Oracle JDK since it’s the basis for the latter. Oracle JDK often contains only minor enhancements and differences.

2. Can I use OpenJDK for commercial projects?

Answer: Absolutely. OpenJDK is open-source and free for personal and commercial use under the GNU General Public License.

3. What is the difference between OpenJDK and JDK?

Answer: JDK (Java Development Kit) is a general term for software development kits that implement the Java platform. OpenJDK is an open-source JDK and the official reference implementation of Java SE.

4. How does OpenJDK handle security updates?

Answer: Security updates in OpenJDK are regularly released. It’s important to keep your version updated to protect against vulnerabilities.

5. Is OpenJDK compatible with all operating systems?

Answer: OpenJDK is compatible with most major operating systems, including Linux, Windows, and macOS. However, checking compatibility with your specific OS version is always good.

6. How can I contribute to OpenJDK?

Answer: You can contribute by participating in mailing lists, submitting patches, or contributing to discussions on the OpenJDK community platforms.

7. Does OpenJDK offer long-term support (LTS)?

Answer: Some versions of OpenJDK are designated as LTS and receive extended support, typically for several years.


  • Fredrik Filipsson

    Fredrik Filipsson brings two decades of Oracle license management experience, including a nine-year tenure at Oracle and 11 years in Oracle license consulting. His expertise extends across leading IT corporations like IBM, enriching his profile with a broad spectrum of software and cloud projects. Filipsson's proficiency encompasses IBM, SAP, Microsoft, and Salesforce platforms, alongside significant involvement in Microsoft Copilot and AI initiatives, enhancing organizational efficiency.