The release of Scala 2.11.1!
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This release contains an important fix for serialization, which was broken in Scala 2.11.0 (SI-8549). The fix necessarily breaks serialization compatibility between 2.11.0 and 2.11.1 (this is separate from binary compatibility, which is maintained).
Users of distributed systems that rely on serialization to exchange objects (such as akka) should upgrade to Scala 2.11.1 (and akka 2.3.3) immediately. We also strongly recommend that libraries that themselves declare classes with @SerialVersionUID annotations release a new version and ask their Scala 2.11 users to upgrade.
We apologize for the breakage. We have included a new suite of tests that will ensure stability of serialization for the remainder of the 2.11.x series.
Compared to 2.11.0, this release fixes 26 issues. We reviewed and merged 51 pull requests.
The next minor Scala 2.11 release will be available in at most 2 months, or sooner if prompted by a serious issue.
The remainder of these release notes summarizes the 2.11.x series, and as such is not specific to this minor release.
Upgrading
Code that compiled on 2.10.x without deprecation warnings should compile on 2.11.x (we do not guarantee this for experimental APIs, such as reflection). If not, please file a regression. We are working with the community to ensure availability of the core projects of the Scala 2.11.x eco-system, please see below for a list. This release is not binary compatible with the 2.10.x series, to allow us to keep improving the Scala standard library.
Required Java Version
The Scala 2.11.x series targets Java 6, with (evolving) experimental support for Java 8. In 2.11.1, Java 8 support is mostly limited to reading Java 8 bytecode and parsing Java 8 source. Stay tuned for more complete (experimental) Java 8 support. The next major release, 2.12, will most likely target Java 8 by default.
New features in the 2.11 series
This release contains all of the bug fixes and improvements made in the 2.10 series, as well as:
Collections
Immutable HashMaps and HashSets perform faster filters, unions, and the like, with improved structural sharing (lower memory usage or churn).
Mutable LongMap and AnyRefMap have been added to provide improved performance when keys are Long or AnyRef (performance enhancement of up to 4x or 2x respectively).
BigDecimal is more explicit about rounding and numeric representations, and better handles very large values without exhausting memory (by avoiding unnecessary conversions to BigInt).
List has improved performance on map, flatMap, and collect.
See also Deprecation above: we have slated many classes and methods to become final, to clarify which classes are not meant to be subclassed and to facilitate future maintenance and performance improvements.
Modularization
The core Scala standard library jar has shed 20% of its bytecode. The modules for xml, parsing, swing as well as the (unsupported) continuations plugin and library are available individually or via scala-library-all. Note that this artifact has weaker binary compatibility guarantees than scala-library – as explained above.
The compiler has been modularized internally, to separate the presentation compiler, scaladoc and the REPL. We hope this will make it easier to contribute. In this release, all of these modules are still packaged in scala-compiler.jar. We plan to ship them in separate JARs in 2.12.x.
