Eclipse: Errors occurred during the build. Errors running builder 'Java Builder'

Question

I'm having an error while trying to make Eclipse Oxygen work in Kubuntu 16.04. Whenever I open a file, and sometimes on Eclipse startup too even if there's no open ones, I get many errors, in particular some I can't copy that occur when I try to use code completion, and most of all this one:

Errors occurred during the build.
Errors running builder 'Java Builder' on project 'MyFirstAfterReinstallAndPlugin'.
java.lang.NullPointerException

I have to specify that this started to occur after I downloaded the extension for Java 9 support and created a new project with the Java_SE9 JRE: before that it would behave in another strange way. Code correction wouldn't find the "System" class and a lot of strange errors happened. I have installed openjdk9 and javac from command line works fine. Plus Eclipse said that I had to have Java 1.8 or superior, making the fact that it didn't work before strange as well.

I've tried everything I found online but still can't figure this out.

Answer 1

Look here:

https://bugs.eclipse.org/bugs/show_bug.cgi?id=498755

Thanks for the report. This has been fixed recently. You may want to try a recent build from http://download.eclipse.org/eclipse/downloads/

This bug has been marked as a duplicate of bug 496675

SUGGESTIONS:

1. Try the latest/greatest update to Eclipse Oxygen

   ... OR ...

2. If that doesn't work, try an OLDER version (e.g. Neon, or even Mars2)

Answer 2

I solved this problem simply by deleting the project causing the trouble, and then re-importing it in Eclipse.

1. Delete the project from the Eclipse workspace.
   (i) Simply 'remove' the project: not delete its files !!

   PROCESS:

   • Right-clic on the project to delete.
   • Context-menu :>Delete
   • DO NOT 'Delete project contents on disk' !!

2. Then, reimport the project.

   PROCESS:

   • menu :>File/>Import
   • />Existing Project into Workspace
   • ...