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IntelliJ IDEA: Issue with opening projects [duplicate]

So, today in the morning I closed down IntelliJ(2017.3.3) after doing some programming as usual and everything worked great. Now suddenly when I try to open any of my projects this is the view I am greeted with:
After searching for a solution for this issue I managed to get the projects working by doing the following steps:
File -> Project Structure -> Modules -> + -> Import -> The project .iml file
File -> Project Structure -> Project -> Project SDK -> Java 8 in my case
File -> Project Structure -> Project -> Project language level -> 8
File -> Project Structure -> Project -> Project compiler output -> The path to the out folder of the specific project(the whole path from D:\ to it)
Navigate to Main class in project structure and alt+enter to add it to run configurations.
Finally able to run the project
Now this would be fine if I had to do it once, configuration corruption or whatever happens, but I have to do this every single time I open a project for some reason. I tried restarting my PC, reinstalling 2017.3.3, installing 2018.1 and the issue persists whatever I do. Also there were no visible errors in relation to this issue in any of the above scenarios, steps, installs and so on.

Well it turns out the issue was related to me using OneDrive to backup my data. I assume OneDrive updated at some point and activated Files On-Demand. The issue is documented here. For me personally a solution that worked was:
Right click the OneDrive tray icon
Click settings
Click the settings tab
Disable the Save space and download files as you use them option under Files On-Demand.
Wait for your files to sync up completely, IntelliJ project load is back to normal.

I tried disabling Themed status bar in Material Theme Advanced Settings and it started working for me.
From: IntelliJ IDEA > Preferences > Material Theme > Advanced Settings > Other Tweaks Tab
Disable "Themed Title Bar" by unchecking the box here.

How to import one Eclipse project as a library into another?

I would like to use one of my eclipse projects in another one. Is there a 'smooth' way to do that, without having to export one as a jar file and importing it into another? Especially since I work on both project simultaneously, I would like the latest changes from the imported project to be automatically built and imported into the other one. Is that possible?

It is possible. Right click on your project -> Build Path -> Configure Build Path. Switch to the Projects tab and add one. It will work as a library.
P.S. You might also want to check this: Creating a java library with Eclipse

Answer to this question explains how to import your own library in eclipse.
Quoting from the answer.
Just have "Project" reference your "Library", on windows the process
is (using menu / tab names)
Go to: Project -> Properties -> Java Build Path -> Projects
Client Add...
Select your "Library" project from the list
Click Ok
Click the other Ok Now your done and you can use import for classes in your "Library"

Import into Eclipse causes error on every line

I have Eclipse on my Windows 8 laptop and on a Windows 7 PC at University. I made some projects at the University and tried to import them at home and there is an error on every single line. It tells me everything cannot be resolved to a type but, as you can see, when I start writing the project from scratch (the second half of the image) I have no such problems.
I apologise, I am new to Eclipse and wonder if anyone can offer any advice. Someone recommended modifying the buildpath settings, I tried to fiddle but could not resolve the problem.

What you are missing are the default Libraries in your project
Try this:
right-click on the EventHandlingDemo Project -> Build Path -> Add Libraries
then select the "JRE System Library" -> Next -> Finish
that should do it!

R.java not being generated

I know this is very widespread problem , but I didn't find solution to my particular case after searching the web for almost one day. I am using Ubuntu 14.04. I have just installed eclipse , ADT and SDK. So I have tried followings but still I get the same error.
Install all possible SDK build tools
Delete gen folder and clean/build the project
Fix all the errors in layout files
Make sure that the path to sdk is correct
Check if appcompat_v7 is added as a library or not
So what can you advise me to do besides these?

I had a similar problem and I fixed by adding
import your.package.name.R
to my activity.
Eclipse by default adds import android.R

You should try with NEXT
rigth click in your projects -> Android Tools -> Fixed project libraries or support library project -> clean or restart. If the above does not work, import the projects said JCODER
What you can also try is to change the android api
Hope that helps

First, You have to make sure all of your XML files are absolutely fine and have no errors.
If no errors found, try changing your Build Target and apply, then change it back. In eclipse do the following:
-> Project -> Properties -> Android -> Project Build Target -> Change the target and click Apply

Eclipse: "The import java.io cannot be resolved"

I have several Android projects in Eclipse, and all is fine, except one (a library) that can not resolve any imports.
The java.io imports do resolve fine in other Android projects in the same workspace, and previously (I haven't used it for over a year) this library worked fine, too.
Any ideas?

Check two things
Eclipse preferences
Check your Eclipse preferences: Java -> Installed JREs
The one that you're using should be marked and it should be a JDK not just a JRE.
Project build path
Also check your project's build path: Right click on the project -> Properties -> Java Build Path
Check in the libraries folder whether the JRE System Library is present and ...
If not add it using Add library -> JRE System Library and then
select the correct one (from an installed JDK).

I am using Maven an this is what I did to re-solve -->
Right click on project
Maven -> Update Project. Make sure you choose 'Force update of Snapshots/Releases'.
Also check the 'clean project', 'update project conf from pom' and 'refresh workspace resource options' and click ok.

The following worked for me:
Close the project and reopen it.
OR
Clean the project ( = rebuilds the buildpath and thereby reconfigures the JDK libraries).

I was missing the JRE Systems Library in my Project Tree.
And navigating to Projects' Build Path and 'Add(ing) Library' worked!

I just ran into this problem with Eclipse 2022-6 and java-17-openjdk-amd64. I just appeared during editing in another file, the same code had worked before.
For me, all settings were correct and none of the above tricks worked. What I then did was completely removing the import command import java.io.Closeable;, saving the file, adding the same import command back at the same place, and saving again. The error disappeared.