import java.io.*;
import java.util.ArrayList;

public class ObjectSchreibenClass {
    
    public static void main(String[] args) {
        String datnam = "/Users/joecze/Downloads/myObjs.ser";
        ArrayList<Object> objArrList = read(datnam);
        write(objArrList, datnam);
    }
    
    @SuppressWarnings("unchecked")
    public static ArrayList<Object> read(String datnam) {
        ArrayList<Object> objArrList = null;
        try (ObjectInputStream in = new ObjectInputStream(new FileInputStream(datnam))) {
            objArrList = (ArrayList<Object>) in.readObject();
        } catch (FileNotFoundException ex) {
            System.out.println("Speicherdatei (noch) nicht vorhanden!");
        } catch (Exception ex) {
            System.out.println(ex);
        }
        return objArrList;
    }
    
    public static void write(ArrayList<Object> objArrList, String datnam) {
        if (objArrList == null)
            objArrList = new ArrayList<Object>();

        objArrList.add(new String("ArrayListgroesse: " + objArrList.size()));
        System.out.println(objArrList);

        try (ObjectOutputStream aus = new ObjectOutputStream(new FileOutputStream(datnam))) {
            aus.writeObject(objArrList);
        } catch (IOException ex) {
            System.out.println(ex);
        }
    }
}