ObjectInputStream cannot cast correctly object

Question

I have 2 classes. In first class, I write a data from List, in the second class, I want read this data and put into listview. It save a data correctly, but when I try to get it, logcat give a error:

java.lang.ClassCastException: pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline$podzialPlanu cannot be cast to pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$podzialPlanu
            at pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$AdapterDlaPlanu.getView(AdapterPlanuProbOffline.java:115)

I can't understand why, because always I get the same type of data.

First class write method:

public void SaveAsFile(List<podzialPlanu> lista){
// lista - List<podzialPlanu> podzialPlanuList2 = new ArrayList<podzialPlanu>();

        try {
            FileOutputStream saveFile = new FileOutputStream(Environment.getExternalStorageDirectory().getPath() + "/" + "planProby.sav");
            ObjectOutputStream save = new ObjectOutputStream(saveFile);

            save.writeObject(lista);

            save.close();


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

And the main class, when I try to get data from this file, and put it into my listview

public class AdapterPlanuProbOffline extends Activity implements Serializable {

    List<String> DzienDataList;
    List<String> GodzinaList;
    List<String> RodzajList;
    List<String> ProgramList;
    List<String> UwagiList;
    List<String> listaDni;
    List<String> listaMiesiecy;
    File plik;


    public class podzialPlanu implements Serializable{
        String DzienData;
        String Godzina;
        String Rodzaj;
        String Program;
        String Uwagi;
    }

    AdapterDlaPlanu nowyAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.listviewy);



        nowyAdapter = new AdapterDlaPlanu();

        ListView listView1 = (ListView) findViewById(R.id.listView1);
        listView1.setAdapter(nowyAdapter);

    }



    public class AdapterDlaPlanu extends BaseAdapter implements Serializable{

        List<podzialPlanu> podzialPlanuList = getData();

        @Override
        public int getCount() {
            return podzialPlanuList.size();
        }

        @Override
        public Object getItem(int position) {
            return podzialPlanuList.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            if(convertView == null){
               LayoutInflater inflater = (LayoutInflater) AdapterPlanuProbOffline.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
               convertView = inflater.inflate(R.layout.planproby,parent,false);
            }



            TextView DzienDataTextView = (TextView) convertView.findViewById(R.id.dzienDataTextView);
            TextView GodzinaTextView = (TextView) convertView.findViewById(R.id.godzinaTextView);
            TextView RodzajZajecTextView = (TextView) convertView.findViewById(R.id.rodzajzajecTextView);
            TextView ProgramTextView = (TextView) convertView.findViewById(R.id.programTextView);
            TextView UwagiTextView = (TextView) convertView.findViewById(R.id.uwagiTextView);




/// here is a problem with getData() method
    DzienDataTextView.setText(getData().get(position).DzienData);
    GodzinaTextView.setText(getData().get(position).Godzina);
    RodzajZajecTextView.setText(getData().get(position).Rodzaj);
    ProgramTextView.setText(getData().get(position).Program);
    UwagiTextView.setText(getData().get(position).Uwagi);



            return convertView;
        }

        public podzialPlanu getPodzialPlanu(int position){
            return podzialPlanuList.get(position);
        }
    }




    public List<podzialPlanu> getData()  {

        List<podzialPlanu> podzialPlanuList2 = new ArrayList<podzialPlanu>();
        List< List<String> > listaGlowna = new ArrayList<List<String>>();


        for( int i = 0; i < 5; i++ ) {
            listaGlowna.add(new ArrayList<String>());
        }

        DzienDataList = new ArrayList<String>();
        GodzinaList = new ArrayList<String>();
        RodzajList = new ArrayList<String>();
        ProgramList = new ArrayList<String>();
        UwagiList = new ArrayList<String>();
        listaDni = new ArrayList<String>();
        listaMiesiecy = new ArrayList<String>();

        try {

            FileInputStream file = new FileInputStream(Environment.getExternalStorageDirectory().getPath() + "/" + "planProby.sav");
            ObjectInputStream restore = new ObjectInputStream(file);

            podzialPlanuList2 = (List<podzialPlanu>) restore.readObject();

            restore.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (StreamCorruptedException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return podzialPlanuList2;
    }

Answer 1

Well, lets look at the exception message:

java.lang.ClassCastException: 
          pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline$podzialPlanu 
cannot be cast to 
          pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline$podzialPlanu

Do you see the difference? Notice that there are two different podzialPlanu classes.

Now if the SaveAsFile method in your Question is the one that created the serialization, then it follows that the List<podzialPlanu> argument type is actually referring to a:

   pl.pawelfrydrych.CHAPS.AdapterPlanuProbOnline.podzialPlanu

rather than

   pl.pawelfrydrych.CHAPS.AdapterPlanuProbOffline.podzialPlanu

---

Yes, so what should I do? If is there serialization, then I can't get this data in another class?

OK, so the real problem is not serialization. You would have the same problem if you skipped the serialize / deserialize step.

The fact is that those two nested classes are unrelated. You cannot cast between unrelated classes. So you either need to:

• use just one inner class
• cast to the correct inner class, or
• make the inner classes related (e.g. using a common interface or superclass) and cast to the common supertype.

Assuming that the inner classes are public, you shouldn't have "access" problems.