java.lang.NullPointerException with JDK 11

[Gabe Lafontant]

I think I _know_ what the source of my issue is but want to ask if anyone else has seen this problem. Prior to purchasing the book, I had installed scala on my local machine. My JDK version is 11 and the scala version I have installed is 2.12.7. I followed the steps in the wiki: 

```

$ chmod a+x ./sbt

$ ./sbt
```

When I execute the last command I receive the NullPointerException. I think this is due to my machine have JDK 11 installed and I should uninstall it and revert to JDK 8. I think the version of Scala in the book is not supported by the JDK version I have. My analysis is based on these findings:

https://docs.scala-lang.org/overviews/jdk-compatibility/overview.html

https://github.com/ProjectSidewalk/SidewalkWebpage/issues/1346

https://stackoverflow.com/questions/32152431/sbt-gives-java-lang-nullpointerexception-when-trying-to-run-simple-hello-exam

Once I got back to an older version of the JDK I think I should be fine. Does that make sense?

[Jeremiah Malina]

I experienced this as well on Xubuntu 20.04 where I had JDK 11 installed. I found this and was able to install JDK 8 and switch to it: https://linuxconfig.org/how-to-install-java-on-ubuntu-20-04-lts-focal-fossa-linux

sbt runs and code compiles now

[Erik van Oosten]

If you want to run on JDK 11 you will need to make sure you have a reasonably recent scala version installed. These work: 2.11.12, 2.12.11 and of course 2.13.2. It wouldn't hurt to use a recent sbt version as well.

Kind regards,
    Erik.

--
Erik van Oosten
https://day-to-day-stuff.blogspot.com/

Op 02-06-20 om 23:39 schreef Jeremiah Malina:

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