Java’s Move to GitHub Set for September

JDK 16 Sources Due to Arrive on GitHub Before September 15 GA of JDK 15

The OpenJDK Community effort to transition the source code of standard Java from Mercurial repositories to Git repositories on GitHub is progressing, with early September set as the target date for this major shift. This move marks a significant milestone in the evolution of Java development and aims to streamline and enhance the management of the Java Development Kit (JDK) source code.

Current plans involve Oracle’s Java Platform Group transitioning the jdk/jdk repository on GitHub, which is presently a read-only mirror, to become the read-write master repository for Java Development Kit (JDK) 16 sources. This transition is scheduled to occur a few weeks prior to the general availability of JDK 15, which is set for September 15. The move to GitHub represents a strategic step in improving the efficiency and accessibility of Java’s development process.

As per Java’s six-month release cycle, JDK 16 is expected to be released in March 2021. The migration of repositories to GitHub has been facilitated through Project Skara. This project has involved exploring alternative source code management and code review options for OpenJDK and transitioning to GitHub to leverage its advantages over Mercurial.

The migration to Git is driven by three primary reasons:

1. Size of Version Control System Metadata: Initial prototypes of converted repositories have demonstrated a significant reduction in version control metadata size. For instance, the .git directory of the jdk/jdk repository is approximately 300 MB, compared to around 1.2 GB for the .hg directory in Mercurial. This reduction helps in conserving local disk space and decreases cloning times, making the development process more efficient.
2. Available Tools: Git benefits from a broader range of tools compared to Mercurial. Most text editors and integrated development environments (IDEs), including Eclipse and Visual Studio, have robust Git integration either natively or through plugins. This widespread tool support facilitates a smoother development experience for Java developers.
3. Available Hosting: Git repositories can be hosted on various platforms, either self-hosted or as a service. Using an external source code hosting provider offers benefits such as improved performance, access to web APIs for developer interaction, and expanded community engagement. This flexibility in hosting options enhances the overall accessibility and management of Java’s source code.

Several Java projects, including OpenJFX, Panama, Valhalla, and Loom, have already been migrated to GitHub. The transition of the main JDK repository represents a key step in aligning Java’s development practices with modern tools and methodologies, ultimately aiming to improve collaboration and efficiency within the Java community.