JSON Example

private static Type type = new TypeToken<ArrayList<Receipt>>() {
    }.getType();

  public static void saveList(Context context) {
        SharedPreferences appSharedPrefs = PreferenceManager
                .getDefaultSharedPreferences(context);
        SharedPreferences.Editor prefsEditor = appSharedPrefs.edit();
      //Simple output for showing that the program is saving
	  Log.d("ReceiptList", "Saving main list...");
        Gson gson = new Gson();
	//MainList is the arrayList that I'm saving
        String json = gson.toJson(mainList);
	//ReceiptList is the identifier that I'm using to retrieve the value
        prefsEditor.putString("ReceiptList", json);
        prefsEditor.apply();
    }


    public static void loadList(Context context) {
        SharedPreferences appSharedPrefs = PreferenceManager
                .getDefaultSharedPreferences(context);
        SharedPreferences.Editor prefsEditor = appSharedPrefs.edit();
      //Simple output for showing that the program is loading
        Log.d("ReceiptList", "Loading main list...");
        Gson gson = new Gson();
        String json = appSharedPrefs.getString("ReceiptList", "");
        mainList = gson.fromJson(json, type);
        if (mainList == null) {
            //Haven't saved before, create a new list
            mainList = new ArrayList<Receipt>();
        }
    }