Specify maven.compiler.source and target versions.
1) Maven version which supports jdk you use. In my case JDK 11 and maven 3.6.0.
2) pom.xml
<properties>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
As an alternative, you can fully specify maven compiler plugin. See previous answers. It is shorter in my example :)
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<release>11</release>
</configuration>
</plugin>
</plugins>
</build>
3) rebuild the project to avoid compile errors in your IDE.
4) If it still does not work. In Intellij Idea I prefer using terminal instead of using terminal from OS. Then in Idea go to file -> settings -> build tools -> maven. I work with maven I downloaded from apache (by default Idea uses bundled maven). Restart Idea then and run mvn clean install again. Also make sure you have correct Path, MAVEN_HOME, JAVA_HOME environment variables.
I also saw this one-liner, but it does not work.
<maven.compiler.release>11</maven.compiler.release>
I made some quick starter projects, which I re-use in other my projects, feel free to check: