How to enable Java 12 preview features with Gradle?

Question

When I tried to build my Java code which has switch expressions using Gradle, it throws this error:

error: switch expressions are a preview feature and are disabled by default. 

I tried running ./gradlew build --enable-preview which didn't work either.

I'm using Gradle 5.3.1.

Answer 1

You need to configure the JavaCompile tasks, so that Gradle passes this option to the Java compiler when compiling.

Something like this should work:

tasks.withType(JavaCompile).each {     it.options.compilerArgs.add('--enable-preview') } 

To run the app/tests we need to add jvmArgs.

Example:

test {     jvmArgs(['--enable-preview']) }