Question

I want my app to hold data from ArrayList in file in between sessions. Class I use implements Serializable. When I debug saving seems to go OK, with no exceptions thrown, and going through the loop the right amount of times. Loading loads just some of entries and then throws EOF Exception. The code is here:

public int saveChildren(Context context){
    FileOutputStream fos;
    ObjectOutputStream os;
    try {
        fos = context.openFileOutput(filename, Context.MODE_PRIVATE);
        os = new ObjectOutputStream(fos);
        for(Child c : children){
            os.writeObject(c);
        }
        os.close();
    }
    catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        return 1;
    }
    catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        return 2;
    }
    return 0;
}

---

public void loadChildren(Context context){

    FileInputStream fis;
    try {
        fis = context.openFileInput(filename);
        ObjectInputStream is;
        is = new ObjectInputStream(fis);
        while(is.readObject() != null){
            Child c = (Child) is.readObject();
            boolean skip = false;
            for(Child ch: children){
                if(ch.getName().equals(c.getName())){ 
                    skip = true;
                }
                if(ch.getNr().equals(c.getNr())){ 
                    skip = true;
                }
                if(ch.getImei() != null){
                    if(ch.getImei().equals(c.getImei())){
                        skip = true;
                    }
                }
            }
            if(!skip){
                children.add(c);
            }
        }
        is.close();
    }catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }catch (StreamCorruptedException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }catch (OptionalDataException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

What causes the errors?

Answer 1

You can directly write the children object into the ObjectOutputStream. ArrayList implements serializable. A second thing you might want to do is flush the stream before closing it with os.flush(). You will have:

os = new ObjectOutputStream(fos);    
os.writeObject(children);    
os.flush();
os.close();

and for reading:

is = new ObjectInputStream(fis);
ArrayList<Child> children = (ArrayList<Child>)is.readObject();
is.close();