How Jack (java Android Compiler Kit) Will Affect Scala Developers

Now with announcement of Jack Google clarified the foreseeable future of Java in relation to Android. But what are the implications to Scala and other JVM-based languages developer

Solution 1:

It’s important to understand that there is 2 tool introduced:

• Jack: A new compiler to replace the complicated javac + proguard + dx

• Jill: A library linker that will be able to link currently compiled libraries (.class) and more. See http://tools.android.com/tech-docs/jackandjill

So it sounds like there is 2 separate problem here:

• Scala compatibility: Scala will not be supported by Jack, as Jack compiles Java source code. However Scala 2.11 compiles to Java 1.6 bytecode and therefore Jill will be able to pick that code and convert to jack files to feed the Jack compiler. See Android N Java 8 features (Jack compiler) and Kotlin interop (Kotlin as the same issue as Scala as it’s a JVM language)

• Java 8, and therefore Scala 2.12+, compatibility: This part is under development, if Jack/Jill supports Java 8, then it will also support Scala 2.12+ (through Jill). If not, Java 8 developers are in the same boat as Scala 2.12 developers. In the case Jack supports Java 8 but not Jill, then Java 8 libraries developers will be in the same boat as Scala 2.12 developers. See https://www.guardsquare.com/blog/DroidconLondon2015

Solution 2:

Google just announced that the Jack toolchain will deprecate the Jack toolchain and Android adds "support for Java 8 language features directly into the current javac and dx set of tools"

Source: https://android-developers.googleblog.com/2017/03/future-of-java-8-language-feature.html

We know how much our Android developer community cares about good support for Java 8 language features, and we're changing the way we support them.

and:

We've decided to add support for Java 8 language features directly into the current javac and dx set of tools, and deprecate the Jack toolchain.

Solution 3:

Joan is correct, but I think Jill will have support for Java 8 at some point to, otherwise it will be impossible to use Java 8 in android libraries that will be consumed by android apps, as they package their code in a jar files inside of aar and I don't see this format change happening anywhere soon. Anyway we can only guess, as Google is currently a blackbox in respect to those kinds of changes.

Revising since new info is out in 2017: jack toolchain is now deprecated and old dex/javac stack will receive java8 support so nothing will change for scala now.