How to force SBT to use Java 8?

Question

How can I force SBT to compile to Java 8 class files. I added scalacOptions += "-target:jvm-1.8" but it gives the following error message:

[error] 'jvm-1.8' is not a valid choice for '-target' [error] bad option: '-target:jvm-1.8' [error] (compile:compile) Compilation failed 

I am using SBT version 0.15.5.

I know I am using Java 8 to compile as I added this to build.sbt, but I still wonder why the scalacOptions fails and I don't know what output the scalac produces.

initialize := {   val _ = initialize.value   if (sys.props("java.specification.version") != "1.8")     sys.error("Java 8 is required for this project.") } 

Answer 1

You need the following on your build.sbt file.

javacOptions ++= Seq("-source", "1.8", "-target", "1.8", "-Xlint")  initialize := {   val _ = initialize.value   val javaVersion = sys.props("java.specification.version")   if (javaVersion != "1.8")     sys.error("Java 1.8 is required for this project. Found " + javaVersion + " instead") } 

Answer 2

Support in scalac for jvm-1.8 was added in 2.11.4.

Scala version (2.11.2) does not support -target:jvm-1.8 option.

$ scala -version Scala code runner version 2.11.2 -- Copyright 2002-2013, LAMP/EPFL  $ scala -target Usage: -target:<target>  where <target> choices are jvm-1.5, jvm-1.6, jvm-1.7 (default: jvm-1.6)  bad option: '-target'  Usage: scala <options> [<script|class|object|jar> <arguments>]    or  scala -help  All options to scalac (see scalac -help) are also allowed.