[intellij-idea] IntelliJ IDEA "cannot resolve symbol" and "cannot resolve method"

What are common causes for IntelliJ IDEA not being able to resolve built-in JVM types and methods? For example, when I mouse over String the tooltip says "Cannot resolve symbol 'String'". It's as if IntelliJ has doesn't know where the JVM is.

By the way, I am running OS X 10.6.6. Everything was working fine until I ran the system update this morning.

I was facing the same problem when import projects into IntelliJ.

for in my case first, check SDK details and check you have configured JDK correctly or not.

Go to File-> Project Structure-> platform Settings-> SDKs

Check your JDK is correct or not.

Next, I Removed project from IntelliJ and delete all IntelliJ and IDE related files and folder from the project folder (.idea, .settings, .classpath, dependency-reduced-pom). Also, delete the target folder and re-import the project.

The above solution worked in my case.

For me, IntelliJ could autocomplete packages, but never seemed to admit there were actual classes at any level of the hierarchy. Neither re-choosing the SDK nor re-creating the project seemed to fix it.

What did fix it was to delete the per-user IDEA directory ( in my case ~/.IntelliJIdea2017.1/) which meant losing all my other customizations... But at least it made the issue go away.

For me, I had to remove the intellij internal sdk and started to use my local sdk. When I started to use the internal, the error was gone.

First check if you have configured JDK correctly:

• Go to File->Project Structure -> SDKs
• your JDK home path should be something like this: /Library/Java/JavaVirtualMachine/jdk.1.7.0_79.jdk/Contents/Home
• Hit Apply and then OK

Secondly check if you have provided in path in Library's section

• Go to File->Project Structure -> Libraries
• Hit the + button
• Add the path to your src folder
• Hit Apply and then OK

This should fix the problem