How to Fix Maven Compilation Errors in a Simple Java 10/11 Project

How can I fix compilation errors in my simple Maven project using Java 10 or Java 11?

When running Maven builds for Java 10 or 11 projects, you may encounter compilation errors particularly associated with the `maven-compiler-plugin`. These errors often occur due to incorrect configurations or incompatible plugin versions. This guide provides troubleshooting steps and solutions to help you resolve these issues effectively.

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.8.1</version>
    <configuration>
        <source>11</source>
        <target>11</target>
        <release>11</release>
    </configuration>
</plugin>

Causes

• Using an outdated version of the Maven Compiler Plugin for the new Java features.
• Incompatibility between project structure and module system introduced in Java 9+.
• Missing necessary dependencies that are required for the test compilation.

Solutions

• Update the Maven Compiler Plugin to a version compatible with Java 10/11. It's recommended to use at least version 3.8.0 for Java 10 or later.
• Ensure that your `pom.xml` includes the necessary dependencies for Java modules and the project is structured correctly for Java 10/11.
• Make sure you are not skipping tests that might be crucial for the compilation process, unless specifically intended.

Mistake: Not updating the Maven Compiler Plugin version when upgrading Java versions.

Solution: Update to at least version 3.8.1 or higher for Java 11 compatibility.

Mistake: Misconfiguring the `module-info.java` file or using it improperly.

Solution: Ensure that the `module-info.java` file adheres to the module system requirements and is devoid of syntactical errors.

Mistake: Skipping tests without ensuring that project requirements are still satisfied.

Solution: Review the dependencies and configurations to ensure that skipping tests won't cause issues.