Question

I am unable to write the ArrayList to a file. I am doing as following, what is the correct way?
If I don’t add ‘pt’ into arraylist, process goes fine and it gets saved.
os.writeObject(arr); – after this line debugger goes to IOException. Code:

//holder class implements Serializable
transient ArrayList<Point> arr;
transient Point pt;
//I've tried without transient, same result 
//
arr = new ArrayList<Point>();
pt = new Point();
p.x = 10;
p.y = 20;
arr.add(pt);
//If I don't add 'pt' into arraylist, process goes fine and it gets saved.
//
String strStorageDirectory = this.getFilesDir() + "/DataFiles";
final File DataStorageDirectory = new File(strStorageDirectory);
File lfile = new File(DataStorageDirectory, "samplefile.bin");
FileOutputStream fos;
    try {
        fos = new FileOutputStream(lfile);
        ObjectOutputStream os = new ObjectOutputStream(fos);
        os.writeObject(arr);//after this line debugger goes to IOException
        //I've tried with os.writeObject((Serializable)arr), same result;
        os.flush();//I've tried removing it, same result
        os.close();
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 1

Instead of keeping Points in ArrayList, you can add two Integers per point. Integer supports Serializable, Point does not.