Why is the object not serialized?

Question

Java

There is a class

public class LinkedListVector implements Vector, Serializable
{
    private class Node
    {
        double value;
        Node next, prev;
    }
    private Node beg;
    private int size = 0;
    private Node current = beg;
    LinkedListVector(){...}
    private Node getEl(int index) throws VectorIndexOutOfBoundsException{...}
    public double get(int number) throws VectorIndexOutOfBoundsException{...}
    public void get(int number, double value) throws VectorIndexOutOfBoundsException{...}
    void add(double _value) {...}
    void del(int index) throws VectorIndexOutOfBoundsException {...}
    public void print(){...}
    public int getLength(){...}
    public double norma(){...}
}

In maine I try to serialize:

LinkedListVector test = new LinkedListVector();
test.add(1);
test.add(2);
test.add(3);
test.add(4);
test.add(5);
FileOutputStream fos = new FileOutputStream(filePath);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(test);
oos.flush();
oos.close();

As a result, the error:

There is another class

public class ArrayVector implements Vector, Serializable
{
    private int length;
    private double [] arr;

    //и дальше идут методы
    // ...

and serialization of ArrayVector objects works fine.
Why doesn't serialization of LinkedListVector objects work?

Answer 1

Learn to read stack traces. It directly says that the inner class of Node is not Serializable, although it should.