How to build Netty 4.1 in IntelliJ for its JDK7+ dependencies?

This is perhaps a dumb question, but how am I supposed to build Netty 4.1 in IntelliJ for its JDK7+ dependencies? If I do a fresh clone of Netty/4.1 and open it in IntelliJ, the build fails due to:

Executing pre-compile tasks...
Loading Ant configuration...
Running Ant tasks...
Running 'before' tasks
Checking sources
Copying resources... [netty-resolver]
Copying resources... [netty-buffer]
Copying resources... [netty-common]
Copying resources... [netty-codec]
Copying resources... [netty-transport]
Copying resources... [netty-handler]
Copying resources... [netty-codec-http]
Parsing java... [netty-common]
java: Errors occurred while compiling module 'netty-common'
Checking dependencies... [netty-common]
Dependency analysis found 0 affected files
javac 11.0.10 was used to compile java sources
Finished, saving caches...
Compilation failed: errors: 48; warnings: 7
Executing post-compile tasks...
Loading Ant configuration...
Running Ant tasks...
Synchronizing output directories...
3/8/21, 8:27 PM - Build completed with 48 errors and 7 warnings in 10 sec, 766 ms

Errors like, e.g.,

.../netty/common/src/main/java/io/netty/util/internal/PlatformDependent.java:141:48
java: cannot find symbol
  symbol:   class ThreadLocalRandom
  location: package java.util.concurrent

This is with the IntelliJ Project SDK set to JDK11 and the project language level set to 11:

I see that individual modules have their language level set lower, but I’m assuming I don’t need to manually modify all of those.

I understand that Netty conditionally checks the JDK version at runtime to determine behavior, but I’m not sure how to fix this in IntelliJ and/or Maven so that I can run unit tests and the like. I’ve been resorting to running unit tests from the command-line, which is not great for debugging.

[Scottmitch]

I’ve experience the same issue. Default configuration resulting in broken project is painful. I wonder if the way we are configuring the pom file (or idea) can be improved, or if this is a idea issue. seems like this will continue to impact folks re-initializing their environment IIUC.

https://www.jetbrains.com/help/idea/java-compiler.html#compiler

By default, this option is selected. IntelliJ IDEA deduces from project settings when the cross-compilation is needed and automatically applies the --release compiler option for Java 9.

[Bennett-Lynch]

Mine was checked (by default). Unchecking it fixed it. I can now build and run tests in the IDE. Thanks @chrisvest!