Error:java: error: invalid source release: 13 using JDK12 with IntelliJ

Question

I am trying to build a project with JDK-12 ea. While trying to execute a sample class:

public static void main(String[] args) {
    Scanner scanner = new Sc         


        

Answer 1

The right way™

The earliest version of IntelliJ that supports switch expressions is version 2019.1, which was released on March 27, 2019. You can get it here: https://www.jetbrains.com/idea/download . You also need JDK 12 of course, and set that as your project SDK.

Then you can set the language level to:

12 (Preview) - Switch expressions

With that, everything should work.

If it doesn't, you might want to check that You've;

• set the project language level, as well as the module language level to the "12 (Preview)"
• set the execution JRE in the run configuration of your application to 12 (or the default, which is the project SDK).
• set the right bytecode version in Settings -> 'Build, Execution, Deployment'/Compiler/Java Compiler. (Leave this fields empty to match the language level)

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Manually configure --enable-preview (no intellisense)

Turning my comment into an answer. You can add the --enable-preview flag to the VM by going to:

Run -> Edit Configurations...

Then selecting your main class from the tree menu on the left, and pasting --enable-preview in the "VM options" box

You can do the same for the compiler by going to:

File -> Settings...

Then in the tree menu under Build, Execution, Deployment -> Compiler -> Java Compiler you can put --enable-preview in the "Additional command line parameters" box:

Note that intellisense still might not work after doing that. I'm still seeing red squiggly lines under the ->s with the error message "unexpected token". But, when I click the run button the class compiles and runs just fine.