Source option 5 is no longer supported. Use 6 or later.

gistfile1.txt

From Issue @regisd @ https://github.com/jflex-de/jflex/issues/400

"""
I think this means that

You are using JDK9 or later
Your project uses maven-compiler-plugin with an old version which defaults to Java 5.
You have three options to solve this

Downgrade to JDK7 or JDK8 (meh)
Use maven-compiler-plugin version or later, because
NOTE: Since 3.8.0 the default value has changed from 1.5 to 1.6
See https://maven.apache.org/plugins/maven-compiler-plugin/compile-mojo.html#target
<plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.0</version> </plugin>

Indicate to the maven-compiler-plugin to use source level 6 and target 6 (or later).
Best practice recommended by https://maven.apache.org/plugins/maven-compiler-plugin/index.html
Also note that at present the default source setting is 1.6 and the default target setting is 1.6, independently of the JDK you run Maven with.
You are highly encouraged to change these defaults by setting source and target as described in Setting the -source and -target of the Java Compiler.

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
            <source>1.6</source>
            <target>1.6</target>
        </configuration>
    </plugin>
or use
  <properties>
    <maven.compiler.source>1.6</maven.compiler.source>
    <maven.compiler.target>1.6</maven.compiler.target>
  </properties>
"""

1. Used option 3 to copy directly into pom.xml file in the <plugins> section
2. mvn compile
3. Successfully seen targets