Retrolambda can not be run under JDK 9

[teras]

If we run retrolambda under Java 9, then this error appears:

java.lang.IncompatibleClassChangeError: Method java.util.stream.Stream.of([Ljava/lang/Object;)Ljava/util/stream/Stream; must be InterfaceMethodref constant
	at net.orfjackal.retrolambda.SystemPropertiesConfig.parsePathList(SystemPropertiesConfig.java:158)
	at net.orfjackal.retrolambda.SystemPropertiesConfig.getClasspath(SystemPropertiesConfig.java:148)
	at net.orfjackal.retrolambda.Retrolambda.run(Retrolambda.java:25)
	at net.orfjackal.retrolambda.Main.main(Main.java:28)

Compared with issue #119 indeed at net.orfjackal.retrolambda.SystemPropertiesConfig.parsePathList(SystemPropertiesConfig.java:158) there is a call to Stream.of which, since retrolamda jar is downgraded, it falls to the same problem.

Apart of the obvious answer ("run retrolambda under Java 8), is there any real solution to this problem?

[luontola]

This problem originates from Retrolambda's build processing itself with Retrolambda so that the Maven plugin, which is Java 6 compatible, can be compiled to call Retrolambda's APIs directly. Some options for fixing this:

• Move those classes that the Maven plugin uses (SystemPropertiesConfig) into another module which is compiled using Java 6 (calling the main method probably needs reflection), and do not run Retrolambda on itself.
• Avoid using the Stream API inside Retrolambda and instead use the streamsupport library.
• Downgrade Retrolambda's code to pre-Java 8.

I'll try out the first option and see how it goes...

[teras]

I think the problem could be easily solved by replacing

        return Stream.of(paths.split(File.pathSeparator))

with

        return Arrays.asList(paths.split(File.pathSeparator)).stream()

at retrolambda/retrolambda/src/main/java/net/orfjackal/retrolambda/SystemPropertiesConfig.java line 158

[luontola]

This has been fixed in Retrolambda 2.5.2

Had this issue in Gradle 4.4.1 - currently the most recent version. Gradle 4.4.1 uses Retrolambda 2.5.1 so I hope they add the fixed version soon. I reported this issue here: Gradle - Issue 3921