How to fix "unsupported class file major version 60" in IntelliJ?

Question

I have a Gradle project in Ubuntu. It's written in Java 14. I have the Java 14 JDK installed. When I build it from the command line, everything works, but no one wants to use a command line! When I open it in IntelliJ IDEA, it throws an error:

* Where:
Initialization script '/tmp/ijmapper.gradle`

* What went wrong:
Could not compile initialization script '/tmp/ijmapper.gradle`.
> Startup failed:
General error during semantic analysis: Unsupported class file major version 60.

followed by a long, unhelpful stack trace that says a lot about Groovy. (The project is not a Groovy project; it's a Java project.)

Major version 60 refers to Java 16, which this project is not using. I've already gone into Project Structure and made sure that it's set to use JDK version 14. But the name "ijmapper" suggests that this has something to do with IntelliJ specifically, and this is likely an IDE problem rather than a project problem.

The mapper file simply says:

if(!ext.has('mapPath')) ext.mapPath = { path -> path}

A simple polyfill, in other words.

What's going on here and how can I fix it?

Answer 1

TL;DR; You need to have the Java version which is compatible with your Gradle version, and configure Gradle to use exactly that version (not older Java, and not even newer version).

---

I fixed this problem by changing the Gradle JVM settings in IntelliJ settings:

• In the Settings/Preferences dialog, go to Build, Execution, Deployment → Build Tools → Gradle.

• Under the Gradle section, change the Gradle JVM option. Select a Gradle JVM which works for you.

  

See Resolve the Gradle JVM version for the existing project

Answer 2

For me, it was fixed by upgrading the Gradle version.

In the file under the directory gradle/wrapper/gradle-wrapper.properties, just change the version number of Gradle. For example, if your Gradle version is 6.3, change this:

distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-bin.zip

to:

distributionUrl=https\://services.gradle.org/distributions/gradle-7.0-bin.zip

It is not available in File → Project Structure → Project for the project I was working with.

Answer 3

Upgrading Gradle version 6.8.3 to 7.0 solved my problem. You can upgrade it:

• Menu File → Project Structure → Project (on the left panel)
• Change to Gradle version 7.0

It works with the Android Gradle plugin version 4.2.0.