I creating a program to work with databases and I am getting the following error when compiling in IntelliJ IDEA. Does anyone why this is happening and how I could solve it?
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6 Answers
The error that you get occurs not on complilation, but when you try to run your application. It happens because Java was not able to find Table.class file inside db subdirectory of the project output directory (classpath).
It can happen for multiple reasons:
- wrong main class selected in the run/debug configuration
Table.javais excluded from compilation (by accident or intentionally because it contained errors and you wanted to skip it while working on other code)- class not compiled because Build step is excluded from from Before launch steps in the Run/Debug configuration
- project is misconfigured and there is no Source root defined for the directory containing
dbsubdirectory Table.javahas incorrectpackagestatement or is located/moved to a different package- project path contains a colon
:on Mac/Linux or semicolon;on Windows, it's used to separate the classpath and will render the classpath invalid. See this thread for details. Note that Finder on Mac may display colons in the path as slashes. - the jar may not execute if one of the dependent jars is digitally signed since the new artifact will include the partial signature of the dependency. See this answer for more details.
- In project structure make sure you have the right Java version for compile.
- there is a known bug that sometimes a Java project created from the Command Line template doesn't work because
.idea/modules.xmlfile references invalid module file nameduntitled104.iml. Fix the module name manually or create a project from scratch and don't use a template. - on Windows "Beta: Use Unicode UTF-8 for worldwide language support" Region Setting is enabled. See IDEA-247837 for more details and workarounds.
- When IntelliJ IDEA is configured to store module dependencies in Eclipse format source root configuration is lost due to a known bug. Configure the module to use IntelliJ IDEA format dependencies as a workaround.
In a properly configured project and with the correct run/debug configuration everything works just fine:
9 Comments
urpi
Thanks! Now it is running, but it gives me a new error. This error says Error java: invalid source release: 1.9. Do you know why this might be happening?
urpi
Thanks for the help! It works now! Can I know why the down vote?
CrazyCoder
I didn't downvote your question (I actually upvoted it), but a lot of people here think that it's off-topic, while FAQ clearly states that questions about "software tools commonly used by programmers" are perfectly valid. Posting screenshots in the question instead of the text of the actual errors is another common reason for downvotes.
adamhurwitz.eth
I had a "/" in my file path. Took me 5 hours to realize :-(
sparkonhdfs
I had the wrong java version loaded. Went to File -> project structure -> project sdk -> select correct version. I have both 9.0 and 1.8 installed, and it took 9.0 by default. The version here had to be the same one as the one in run configuration.
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- the jar may not execute if one of the dependent jars is digitally signed since the new artifact will include the partial signature of the dependency. See this answer for more details.
I must again emphasis the point CrazyCoder has here.
The (Oracle) JVM used to throw a SecurityException when you tried to run a Jar-File containing broken signatures. This made sense from a "What's wrong"-Point of view.
That is no longer the case. They are indeed throwing ClassNotFoundExceptions now - even if the class is right there in the file (no matter if it is in the default package/toplevel or way down in a nested package structure).
Comments
Here's what worked for me:
I deleted .ide folder, .iml file. And all other auto generated files by intelliJ then restarted my ide and I was asked if I want to make my project run with maven that's it.
Obviously I said yes :)
1 Comment
laszlo
where such directory can be found?
This is a known bug in the IntelliJ idea. To fix this I just deleted the .iml and the .idea and restart the IDE. It works for most of the cases
Edit: The files will be in the project directories.
2 Comments
laszlo
where are those directories?
Vedant Matanhelia
In the project folder @laszlo sorry for not telling where the filed would be
In my case the default console app template works only if the project folder path does not contain underscore (_) in it. Underscore brings the error
Error: Could not find or load main class com.company.Main
Caused by: java.lang.ClassNotFoundException: com.company.Main
IntelliJ IDEA 2021.3.1 (Ultimate Edition) Build #IU-213.6461.79, built on December 28, 2021
3 Comments
Dance-Henry
omg, I never thought this could be the reason. I spent tons of hours to research and try different ways. None of those worked until your answer. Thanks!
Raihanul Alam Hridoy
My folder doesn't have any underscore. It still doesn't work.
Burst
@RaihanulAlamHridoy, it's about the path to the folder (i.e. any folder in the absolute path to your project folder).
If you've tried everything else that others have suggested (deleting .idea folder, rebuild, etc) there's another place to check, especially if you've built an artifact jar. When you first build an artifact jar, IntelliJ adds a folder: META-INF to src directory. in it is a single file: MANIFEST.MF which has info pointing to the Main-Class for Java to find. If you've refactored your project package, unfortunately IntelliJ does not update this file with the new changes. My MANIFEST.MF has the following correct content:
Manifest-Version: 1.0
Main-Class: org.umoja4life.fatashibackend.MainKt
Where "org.umoja4life.fatashibackend" is the package name, and "MainKt" is IntelliJ's constructed name for a (pseudo) "Main Class" because fun main() has been defined in file "main.kt" in the package directory.
Newbies: btw, This will be confusing for you because there should be no actual "class Main {}" definition despite the error message stating there should be.
Before I discovered this file and after trying everyone else's suggestions, I found it quickest to just have IntelliJ start a project (with correct package name!), initialize it with a trivial main.kt having:
fun main() { println("hello world!") }
run and test that; then, I added back in all my other files, rebuilt, ran, and tested it. Apparently IntelliJ has some secret state information stored somewhere which doesn't get correctly updated if your refactor your package name for an already running project and jar.
