The similar issue was report in

Yesterday, I updated IDEA to newer version, I'm not sure what was the reason but I started getting wired IDE errors.

So I invalidated the cache and restarted the IDE,

When that did not solve the issues, I manually deleted following folders

1. All ~/AppData/*/JetBrains folders .
2. .idea folder inside project root.
3. project-name.iml file inside project root.

After that I updated all intelliJ setting same as above, but Since then I've been getting Cannot resolve symbol 'String' Strangely all other JDK classes are detected, but in whole code String is not working.

CodePudding user response：

It's a known issue specific to IBM JDK.

The workaround is to manually add vm.jar file from JDK_HOME\jre\bin\default\jclSC180\vm.jar to the SDK classpath tab in IntelliJ IDEA.