JavaOne 2010 – OpenJDK BOF

The OpenJDK BOF was an informal Q&A session, attendees were free to ask JDK-related questions and Kelly O’Hair, Dalibor Topic and Mark Reinhold were there to answer. I think that this setup was appropriate for such a sensitive topic given the degree of anxiety of the Java community and probably the state of mind of the former Sun employees themselves. I will try to capture the most relevant  Questions and Answers.

1. Will the JRockit VM get open-sourced? No, the plans are to keep HotSpot open-sourced as Open JDK 7 and add to it some of JRockit unique features by mid 2011.
2. Will Oracle keep going through the JCP? The plans are to keep using the JCP for OpenJDK 7 features such as the Lambda project and even for Java SE 8. No other guarantees were made beyond that.
3. Comment on JDK 7 v/s Open JDK 7: Sun used to provide the OpenJDK + some of its own proprietary binaries (themselves largely based on the OpenJDK, such as plugins) gratis (as in free beer). Oracle will continue doing so in OpenJDK 7 and at the same time provide JDK 7 which should be 98% identical to OpenJDK 7.
4. Will Oracle make some performance-sensitive features (such as sockets, io) part of JDK 7 as opposed to OpenJDK 7? No because Oracle has little/nothing to gain from such a model. It would only defragment the  code base and make the merge back into an OpenJDK a nightmare. On the other hand JRockit Mission Control API will remain proprietary but some of its features will make it to the Open JDK such as the pluggable verbose logging and the JMX management tool (it can handle port numbers while the JMX on the HotSpot currently can’t).
5. Will the deterministic GC of JRockit make it to OpenJDK? No because there are currently paying customers that Oracle would like to keep as such. On the other hand certain aspects of the JRockit GC could make it such as incremental sliding compaction.
6. Will the Da Vinci code continue to thrive? Yes, unfortunately not all of John Rose great ideas can/will make it to OpenJDK 7. For now JSR 292 (Lambda project – closures) will make it. The rest, most notably support for tail recursion, will not.
7. What’s the state of Jigsaw? It’s in a state of flux, we’re not at a point where we can readily start portions of the JDK. But it is actively worked on for OpenJDK 7.
8. What about Project Verrazano? For now it is a research project (it takes a JAR and a platform spec, modularizes the classes themselves to reduce their code size to an optimal one).
9. What about OpenJDK 6? Actually the effort was started after the one for OpenJDK 7 and so it did not start with the Java SE 6 code base, rather it started with the OpenJDK 7 code base and engineers started removing features to match JDK 6. It slightly differs from JDK 6, depending on the particular repository but the main features such as CORBA, JAXB, JAXP and JAX-WS, when they differ, do so very little, and usually only in terms of exact licensing. Currently there are are only four different features between JKD 6 and OpenJDK 6: Graphics, Fonts (the most prominent one), SNMP and Color Management.
10. Speaking of repositories, which distributed SCM do you recommend? The Solaris team opted for Mercurial (Python-based), it’s great, we could have gone with Git but not sure what to do about the added complexity

So there you have it, the latest on OpenJDK 7; the session started slow with few questions but as time went by the audience asked more and more questions, mostly I think to get reassured about the open-source fate of OpenJDK. The message was indeed a reassuring one, but one thing remains to be seen is: What will happen to Java SE post 2012?

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