How to use a library that not specifies modules in Java?

Question

I've recently returned to Java development since a very long time, and I'm trying to upgrade an old project to a newer Java version. This project uses the EJML library, but I can't seem to get rid of the error messages in Visual Studio Code. I've distilled the problem that I'm facing into a minimal working example exhibiting the issue.

This example consists of three files:

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>mwe</groupId>
    <artifactId>mwe</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>1.17</maven.compiler.source>
        <maven.compiler.target>1.17</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-all</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-core</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-cdense</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-ddense</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-fdense</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-zdense</artifactId>
            <version>0.43.1</version>
        </dependency>
        <dependency>
            <groupId>org.ejml</groupId>
            <artifactId>ejml-simple</artifactId>
            <version>0.43.1</version>
        </dependency>

    </dependencies>
</project>

src/main/java/module-info.java

module mwe {
    requires ejml.all;
    requires ejml.core;
    requires ejml.cdense;
    requires ejml.ddense;
    requires ejml.fdense;
    requires ejml.zdense;
    requires ejml.simple;

    exports mwe;
}

src/main/java/mwe/Main.java

package mwe;

import org.ejml.data.DenseMatrix64F;
import org.ejml.ops.CommonOps;

public class Main {
    public static void main(String[] args) {
        double[][] aArray = new double[][] {
            {1, 1}, 
            {1, 2}
        };
        DenseMatrix64F a = new DenseMatrix64F(aArray);
        DenseMatrix64F t = new DenseMatrix64F(2, 2);

        CommonOps.invert(a, t);
    }
}

The error messages that I can't get rid of start by stating that the imports cannot be resolved, and as a consequence I also get error messages on the lines where I use this classes stating that they cannot be resolved to a type.

I've tried various variants (e.g. only having ejml-all as a dependecy), but the error messages remain. I don't even know if this is actually fixable without rebuilding the library to include module info, but since I am not the owner of EJML, I don't think that is the ideal way to solve this.

Am I missing something? Is there an easy solution? Is this merely an issue of using Visual Studio Code, or will this also be the case with other editors?

Answer 1

I haven't used ejml. I think you don't have to create the module-info.java. And the ejml replaced DenseMatrix64F with DMatrixRMaj. You can try like this:

double[][] aArray = new double[][]{
            {1, 1},
            {1, 2}
};
DMatrixRMaj a = new DMatrixRMaj(aArray);
DMatrixRMaj b = new DMatrixRMaj(2, 2);
CommonOps_DDRM.invert(a, b);