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Brand new to Eclipse using Java. HelloWorld spawns immediate error. [message #1805382]

Fri, 12 April 2019 21:00

Missing name Mising name

Messages: 12
Registered: January 2010

Junior Member

Using Eclipse 2019-03 (4.11.0); build id: 20190314-1200
Java sdk 12
MacOS 10.3.6

Opened eclipse after install.
I followed the "Create HelloWorld application" guided-walkthrough. Immediately after I created the Java project HelloWorld, it gave me a build error: Errors occurred during the build.
Errors running builder 'Java Builder' on project 'HelloWorld'.
java.lang.NullPointerException

So I deleted the project and deleted all files from my "eclipse-workspace" (so it was empty) and I tried again. Now, immediately after I click "finish" on the guided walkthrough for the "Create HelloWorld application", I get the following error:
"Periodic Workspace save.' has encountered a problem. Could not write metadata for '/'
Detailed info: "Could not write metadata for '/'.
/Users/dJames/eclipse-workspace/.metadata/.plugins/org.eclipse.core.resources/.root/.markers.snap (No such file or directory)"

And it is true when I check for that directory, there is a folder "org.eclipse.org.resources" which only contains two items: a "projects" folder, and a file: "0.snap", but not the ".root" folder.

Since I got a different error than the first time I tried to load the HelloWorld application, it seems like I have deleted something important when I emptied the "eclipse-workspace" folder, but I really don't know how to return it to good.

Any help with the two problems above, greatly appreciated.
Jim

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Re: Brand new to Eclipse using Java. HelloWorld spawns immediate error. [message #1805390 is a reply to message #1805382]

Sat, 13 April 2019 02:47

Ed Merks

Messages: 33140
Registered: July 2009

Senior Member

Don't ever touch anything in the <workspace>/.metadata folder unless you know exactly what you are doing. If you've corrupted something there, best you create a new workspace in a new location (or move the broken one to a different location and create a new one at the old location). You can use File -> Import... -> General -> Existing Projects into Workspace to import your projects from the broken workspace into a clean new workspace.

Ed Merks
Professional Support: https://www.macromodeling.com/

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Re: Brand new to Eclipse using Java. HelloWorld spawns immediate error. [message #1805414 is a reply to message #1805382]

Sun, 14 April 2019 20:31

Missing name Mising name

Messages: 12
Registered: January 2010

Junior Member

Thanks for that information.

Also, I resolved my original problem about the nullpointer exception:
This error was thrown during building but there was an additional error highlighted in the Eclipse IDE at line 1 (before any of my java code) of my HelloWorld program:
"must declare a named package eclipse because this compilation unit is associated to the named module HelloWorld."

This was resolved by deleting the "module-info.java" per the following thread:

https://stackoverflow.com/questions/53033899/must-declare-a-named-package-eclipse-because-this-compilation-unit-is-associated

Thanks,
Jim

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