To enable preview feature you must define –enable-preview in pom.xml. I’am using java 14
In pom.xml, specify your java compiler version
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>14</maven.compiler.source>
<maven.compiler.target>14</maven.compiler.target>
</properties>
Next in pom.xml, Edit like below to add compiler arguments (–enable-preview)
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<release>14</release><!--Java Version-->
<compilerArgs>
<arg>--enable-preview</arg>
</compilerArgs>
</configuration>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
<configuration>
<argLine>--enable-preview</argLine>
</configuration>
</plugin>
Now execute the below maven command
mvn clean verify
Thats it. Hope this helps