Intellij Cannot resolve symbol on import

问题:

This problem happens intermittently for different libraries and different projects. When trying to import a library, the package will be recognized, but the class name can't be resolved.

If on the import statement, I right-click -> Goto -> the package's declaration, I see all the decompiled classes displayed in the side pane -- Including the ones I need -- If I try to auto-complete the import statement, I notice the class I need is not featured in the dropdown.

I tried invalidating caches already, doesn't work. I cannot find any class conflicts -- there is no other jar file in my classpath with the same package name. I am able to import this class into other projects.

Please see screen shots:

Anyone have a clue?

回答1:

you can try invalidating the cache and restarting intellij, in many cases it will help.

File -> Invalidate Caches/Restart

回答2:

There can be multiple reasons for this. In my case it was wrong source root issue. Invalidate caches didn't work along with other solutions.

Check your module source roots.

1. Project Structure (Ctrl+Alt+Shift+S).

2. Modules

3. Select your problem module.

4. Change tab on top of window "Sources".

5. Remove unwanted source roots. Keep one and add src and test source roots in this root.

回答3:

I faced a similar issue, Mike's comment helped me move in the direction to solve it.
Though the required library was a part of the module in my project too, it needed a change of scope. In the module dependency, I changed the scope to "Compile" rather than "Test" and it works fine for me now.

回答4:

Check your module dependencies.

1. Project Structure (Ctrl+Alt+Shift+S).
2. Modules
3. Select your problem module.
4. Change tab on top of window "Dependencies".
5. Check what needed library (maybe, you need to add specified library in the tab 'libraries') or module has listed here and it has right scope ('complile' mostly).

回答5:

IntelliJ has issues in resolving the dependencies. Try the following:

1. Right click on pom.xml -> Maven -> Reimport
2. Again Right click on pom.xml -> Maven -> Generate sources and update folders

回答6:

File -> Invalidate Caches/Restart or rebuilding the project did not work wor me.

What worked for my Gradle project was to "Refresh all Gradle projects" from the Gradle tab on top-right corner of IntelliJ v2017, using the yellow marked button shown below:

回答7:

I tried invalidating caches and restarting, but the only thing that worked for me was wiping out the .idea directory completely, then creating a new project from scratch.

回答8:

I also got this error for multiple times when I try to build a new java project.

Below is the step how I got this stupid issue.

1. Create an empty project, and create new directory src/main/java.
2. Create the source package net.gongmingqm10.sketch.
3. Use gradle wrapper, gradle idea to build the gradle stuff for the project.
4. Add some dependencies in build.gradle file, and gradle build, reimport the project.
5. Create User.java and School.java in the existing package net.gongmingqm10.sketch
6. I got the error while I try to use import School in User.java.
7. Intellij keeps complain can not resolve symbol on import.

Solution:

Build the project first, and mark the main/java as the source root. Create a new directory with the same name net.gongmingqm10.sketch. Move all the files from the old troubling packages to new package.

Root cause:

Directory tree of source code

As you can see from the tree. I got a directory named net.gongmingqm10.sketch. But what we really need is the 3 levels directory: net->gongmingqm10->sketch

But before I finish building my project in Intellij, I create new directory named net.gongmingqm19.sketch, which will give me a real directory with the name net.gongmingqm10.sketch.

When we trying to import it. Obviously, how can intellij import the file under the weired directory with the name a.b.c.

回答9:

I found the following answer from @jossef-harush and @matt-leidholm useful from another link

• in IntelliJ editor, click on the red keyword (Integer for example) and press ALT + ENTER (or click the light bulb icon)
• select Setup JDK from the intentions menu

• click on Configure

• In my case, the JDK path was incorrect (pointed on /opt/jdk1.7.0_51 instead of /opt/jdk1.7.0_65)

• click on the ... and browse to the right JDK path

• let's clear the cache

回答10:

File -> Invalidate Caches/Restart And Build your project

回答11:

Right click on pom.xml file, go to Maven click on Reimport. I had similar problem and this worked for me.

回答12:

Simple Restart worked for me.

I would suggest first try with restart and then you may opt for invalidating the cache.

PS : Cleaning out the system caches will result in clearing the local history.

回答13:

I had a similar issue with my imported Maven project. In one module, it cannot resolve symbol on import for part of the other module (yes, part of that module can be resolved).

I changed "Maven home directory" to a newer version solved my issue.

Update: Good for 1 hour, back to broken status...

回答14:

I found the source cause!

In my case, I add a jar file include some java source file, but I think the java source is bad, in Intellij Idea dependency library it add the source automatic, so in Editor the import is BAD， JUST remove the source code in "Project Structure" -> "Library", it works for me.

回答15:

What did it for me is to edit the package file in the .idea folder as I accidentally added sources to this jar library and android couldn't resolve it by deleting the sources line as marked in the b/m picture library error.

Then rebuild the gradle and bam problem solved.

回答16:

I had the same issue and the reason for that was incorrect marking of the project's sources.

I manually created the Root Content and didn't notice that src/main/test folder was marked as Sources instead of Tests. So that is why my test classes were assumed to have all their test libraries (JUnit, Mockito, etc.) with the scope of Compile, not Test.

As soon as I marked src/main/test as Tests and rebuilt the module all errors were gone.

回答17:

@Anton Dozortsev I was driven crazy by a similar behavior; I ended up re-installing the IDE a bunch of times, only getting past the issue after removing the IDEA app, all caches, preferences, etc.

I tried all kinds of steps in the interim, (like restarts, invalidations, deleting .idea and *.iml files, and others.)

Turns out, the problem was due to IntelliJ's idea.max.intellisense.filesize setting. I had set it to 100KB, which was smaller than my dependency's size, leading to IntelliJ showing it as unknown, just like in your screenshot.

Fix:

1. Click on Help -> Edit Custom Properties

2. Set the property to a larger value; the default is 2500KB idea.max.intellisense.filesize=2500

回答18:

I had this recently while trying to use Intellij to work on NiFi, turned out the issue was that NiFi requires Maven >= 3.1.0 and the version that I'd checked out with (I guess my default) was 3.0.5. Updating the Maven version for the project fixed it, so in some cases Maven version mis-alignment can be a thing to look...I'd guess it's fairly unusual but if you get this far on the thread you're probably having an unusual issue :)

回答19:

The same problem. If these methods not work. you can try to delete the lib from local maven repository, and reimport to pom .

Finally it' fine for me.

回答20:

Had the same problem till I noticed that the src folder was marked as root source instead of java! Changing to only the java (src/main/java) to be the source root solved my problem

回答21:

file-> Project Structure -> Modules, find the module with problems, click it and choose the Dependencies tab in the right side. Click the green plus sign, try to add the jar or libraries that cause the problem. That works for me.

回答22:

Missing io? Try import org.openide.util.io.ImageUtilities.