|JDK 9 Update
|Written by Kay Ewbank
|Monday, 08 December 2014
Oracle has announced more updates to the next version of Java, alongside an early access build of JDK 9 with Jigsaw.
Project Jigsaw has been long promised as a way to let Java programmers write code consisting of independent modules. The goal of Jigsaw is to define a standard module system for the Java platform and use that to modularize the platform itself and applications. Jigsaw was intended to be included in Java 8, but missed that so is now proposed for Java 9.
In a post to the OpenJDK mailing list, Mark Reinhold, chief architect for the Java platform group at Oracle, said that early adopter builds of JDK with Jigsaw are now available. The builds are based upon the Jigsaw m2 forest, in which the developers are working to implement modular run-time images as described in JEP 220. The current build implements all the changes described in that JEP except that the jrt: file-system provider is not yet implemented, and the extension mechanism has not yet been removed.
These bundles are meant to allow developers to try out Project Jigsaw without needing to build it from sources. The builds are available from the JDK 9 Project Site.
Alongside the appearance of Jigsaw, changes have also been made to some of the JEPs. JEPs, Java Enhancement Proposals, are being used to let new features be discussed and developed without going through a full formal specification (JSR). JEPs that are popular and successful will be put forward as part of the next full formal specification.
The updated JEPs provide unified JVM logging and more compiler controls.
Unified JVM Logging (JEP 158) ) will give a common logging system for all JVM components. This will change the current way the JVM reports events in its subsystems and add common logging command-line options for loggers. This JEP was heavily influenced by what exists in Oracle's JVM JRockit, according to the proposal.
The second JEP to be updated, JEP 165, proposes to improve control of the JVM compilers by encapsulating control into a set of options. It would allow different option sets to be applied depending on which method is being compiled, and opens up the possibility of changing the option sets during run time.
Garbage collection combinations are to be tidied up, with deprecated GC combinations being removed, according to JEP 214. This is essentially taking out the outdated garbage collection combinations removed in Java 8. Losing the combinations will hopefully free up enough resources to simplify the HotSpit GC code, so reducing bugs and improving other GC combinations.
Project Coin is the focus of the final update (JEP 213). The summary of this JEP says that the small language changes included in Project Coin have been easy to use and have worked well in practice, but that several amendments could address a few rough edges of those changes.
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