Main

package file.example;
import java.io.*;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class Main {

    private static String dir = "src/";
    private static String file = "file";

    public static void main(String[] args) {
        try (
                ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(dir.concat(file)));
                ObjectInputStream is = new ObjectInputStream(new FileInputStream(dir.concat(file)))) {
            List<Serializable> list = new ArrayList<>();
            list.add(new Individual("Deivid", 15));
            list.add(new Individual("Ivan", 18));
            list.add(new Individual("Petio", 15));

            int counter = 0;
            for (Serializable el : list) {
                os.writeObject(el);
                counter++;
            }
            list.clear();

            for (int i = 0; i < counter; i++) {
                Serializable inf = (Serializable) is.readObject();
                list.add(inf);
            }

            list.forEach(System.out::println);

        } catch (IOException |
                ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}