How do I seralize Primitive64Matrix in OjAlgo?

I'm working on a image classification library, in 100% Java. It does not include deep neural networks. It uses Fisherfaces by OjAlgo. jFaces works very similar to regular machine learning software. Train model and validate it. I want to serialize the model and the model contains only objects of Primitive64Matrix

https://github.com/DanielMartensson/jFaces

How can I serialize Primitive64Matrix in OjAlgo?

I have my class

public class Model implements Serializable{
    private String name;
    //private Primitive64Matrix D;
    private Primitive64Matrix W;
    private Primitive64Matrix P;
    //private long num_components;
    private Primitive64Matrix mu;
    private Primitive64Matrix y;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Primitive64Matrix getW() {
        return W;
    }
    public void setW(Primitive64Matrix w) {
        W = w;
    }
    public Primitive64Matrix getMu() {
        return mu;
    }
    public void setMu(Primitive64Matrix mu) {
        this.mu = mu;
    }
    public Primitive64Matrix getP() {
        return P;
    }
    public void setP(Primitive64Matrix p) {
        P = p;
    }
    public Primitive64Matrix getY() {
        return y;
    }
    public void setY(Primitive64Matrix y) {
        this.y = y;
    }

}

Then I try to save it:

static public void saveModel(Model model,String modelPath) {
    try {
         FileOutputStream fileOut = new FileOutputStream(modelPath);
         ObjectOutputStream out = new ObjectOutputStream(fileOut);
         out.writeObject(model);
         out.close();
         fileOut.close();
         logger.info("Model saved at " + modelPath);
      } catch (IOException e) {
         e.printStackTrace();
      }
}

I get the error:

java.io.NotSerializableException: se.danielmartensson.fisherfaces.Model
    at java.base/java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1185)
    at java.base/java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:349)
    at se.danielmartensson.fisherfaces.tools.SaveLoad.saveModel(SaveLoad.java:22)
    at se.danielmartensson.Main.main(Main.java:123)
Exception in thread "main" java.lang.NullPointerException
    at se.danielmartensson.Main.main(Main.java:127)

OjAlgo is 100% Java, so this must work? Right?

In Java only objects that implement the Serializable interface are serializable...

ojAlgo classes rarely implements Serializable nor is there a defined matrix file format or similar.

You have to build something yourself.