IntellJ IDEA “cannot resolve symbol” and “cannot r

问题:

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.

回答1:

Most likely JDK configuration is not valid, try to remove and add the JDK again as I've described in the related question here.

回答2:

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

回答3:

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.