How do I serialize an object and save it to a file in Android?

Question

Say I have some simple class and once it's instantiated as an object I want to be able to serialize its contents to a file, and retrieve it by loading that file at some later time... I'm not sure where to start here, what do I need to do to serialize this object to a file?

public class SimpleClass {    public string name;    public int id;    public void save() {        /* wtf do I do here? */    }    public static SimpleClass load(String file) {        /* what about here? */    } } 

This is probably the easiest question in the world, because this is a really simple task in .NET, but in Android I'm pretty new so I'm completely lost.

Answer 1

Saving (w/o exception handling code):

FileOutputStream fos = context.openFileOutput(fileName, Context.MODE_PRIVATE); ObjectOutputStream os = new ObjectOutputStream(fos); os.writeObject(this); os.close(); fos.close(); 

Loading (w/o exception handling code):

FileInputStream fis = context.openFileInput(fileName); ObjectInputStream is = new ObjectInputStream(fis); SimpleClass simpleClass = (SimpleClass) is.readObject(); is.close(); fis.close(); 

Answer 2

I've tried this 2 options (read/write), with plain objects, array of objects (150 objects), Map:

Option1:

FileOutputStream fos = context.openFileOutput(fileName, Context.MODE_PRIVATE); ObjectOutputStream os = new ObjectOutputStream(fos); os.writeObject(this); os.close(); 

Option2:

SharedPreferences mPrefs=app.getSharedPreferences(app.getApplicationInfo().name, Context.MODE_PRIVATE); SharedPreferences.Editor ed=mPrefs.edit(); Gson gson = new Gson();  ed.putString("myObjectKey", gson.toJson(objectToSave)); ed.commit(); 

Option 2 is twice quicker than option 1

The option 2 inconvenience is that you have to make specific code for read:

Gson gson = new Gson(); JsonParser parser=new JsonParser(); //object arr example JsonArray arr=parser.parse(mPrefs.getString("myArrKey", null)).getAsJsonArray(); events=new Event[arr.size()]; int i=0; for (JsonElement jsonElement : arr)     events[i++]=gson.fromJson(jsonElement, Event.class); //Object example pagination=gson.fromJson(parser.parse(jsonPagination).getAsJsonObject(), Pagination.class);