eclipse stuck when building workspace

I was able to fix this with the following:

First, exit Eclipse. Then temporarily move the following .projects folder to a safe location:

mv .metadata\.plugins\org.eclipse.core.resources\.projects projects

Start and exit Eclipse, then move the .projects folder back to where it was originally:

mv projects .metadata\.plugins\org.eclipse.core.resources\.projects

Use at your own risk, of course.

Some time it's very helpful to execute eclipse from command line with "-clean" parameter to enforce it produce clean up for workspace.

You may want to take a look at How to report a deadlock. You may also want to check the Error view and/or the error log ([workspace]/.metadata/.log). If that doesn't help, you'll probably need to include more info about which plugins you have installed and which projects you have. Can you create a minimal workspace which reproduces the problem?

I just restarted eclipse and it started working the next time.

I was able to solve this by removing extra folder that Eclipse had created in my eclipse installation folder. I didn't install and I was using Eclilpse Neon 3 with Spring Tool suite also installed. But, when I looked into extracted eclipse installation, I had C: folder which had some folder structure. It was mirror image of my Downloads folder. I removed it and restarted.

It worked for me!

Rather than debug and find the exact root cause(s) for this, I just deleted the projects and the metadata folder. Eclipse will rebuild the .metadata file the next time it's launched.

I then pulled in the latest project code and the problem was solved. It was more work as I had to reconfigure everything, including my servers, but build workspace had been stopping at 50% for anywhere from 3 to 5 minutes before it would completely finish, so it was worth the effort.

Also, I've found that with Eclipse, if you stop the build workspace before it completes and shut down Eclipse if that hangs up everything, you can really mess up your configuration and waste lots of time trying to get it stable again. I'm using Eclipse Oxygen, but I've had this happen in all the versions of Eclipse I've used, so I really try to avoid it, if possible.

Inside the project folder open .project file. There is a bad entry and it might help

    <buildCommand>
        <name>org.eclipse.m2e.core.maven2Builder</name>
        <arguments>
        </arguments>
    </buildCommand>

If you are using Maven as a build tool you might want to:

1. Close eclipse

2. Delete dependency directories located in .m2/repository/ - in Linux it's located under Home directory and in Windows it should be in c:\Users<YourUsername>.m2 (replace '' with your username)

3. Start Eclipse and enjoy normal work :)

That helped me resolve this issue and I hope it helps you too. :)
Cheers!

P.S. I've edited my answer (as @howlger asked) where it was also suggested to delete .eclipse and .p2 folders as it can do harm (although it did NOT in my case + I had to reinstall some of plugins I'm using).

In case there is a problem on start when building your project disable the build automatically from menu. Project -> Build Automatically. This solved my problem while more sophisticated solutions could not.

This can also happen if you have an empty java file that is named and classpath-located exactly like another java file (which can happen when resolving merge conflicts for moved resources).

For example, the following setup causes this issue in a multi-maven module:

• module1/src/main/java/com/package/MyClass.java (empty)
• module2/src/main/java/com/package/MyClass.java (actual valid class)

To fix, simply delete the empty java file.