How to fix maven compiler errors

POM.xml

<build>
    <pluginManagement>
        <plugins>
            <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-compiler-plugin -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                </configuration>
            </plugin>
        </plugins>
    </pluginManagement>
</build>