正确的方法™

支持开关表达式的IntelliJ最早版本是2019.1版本，该版本于2019年3月27日发布.您可以在此处获取: https://www.jetbrains.com/idea/download .当然，您还需要JDK 12，并将其设置为项目SDK.

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.

然后您可以将语言级别设置为:

Then you can set the language level to:

12 (Preview) - Switch expressions

有了它，一切都会正常工作.

With that, everything should work.

如果没有，则可能要检查您是否已经拥有；

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

• 将项目语言级别以及模块语言级别设置为"12(预览)"
• 在应用程序的运行配置中将执行JRE设置为12(或默认值，这是项目SDK).
• 在设置"中设置正确的字节码版本-> 构建，执行，部署"/编译器/Java编译器. (将此字段保留为空以匹配语言级别)

将我的评论变成答案.您可以通过以下操作将--enable-preview标志添加到VM:

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

运行-> 编辑配置...

然后从左侧的树菜单中选择您的主类，然后将--enable-preview粘贴到"VM options"(虚拟机选项)中.盒

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

您可以通过以下步骤对编译器执行相同操作:

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

文件-> 设置...

然后在树菜单中的 Build，Execution，Deployment ->下. 编译器-> Java编译器，您可以将--enable-preview放入其他命令行参数"框:

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

请注意，执行此操作后，Intellisense仍然可能无法正常工作.我仍然在->下看到红色的波浪线，并显示错误消息意外的令牌".但是，当我单击运行按钮时，该类将编译并运行正常.

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.