Save ArrayList to SharedPreferences

Question

I have an ArrayList with custom objects. Each custom object contains a variety of strings and numbers. I need the array to stick around even if the user leaves

Answer 1

I used the same manner of saving and retrieving a String but here with arrayList I've used HashSet as a mediator

To save arrayList to SharedPreferences we use HashSet:

1- we create SharedPreferences variable (in place where the change happens to the array)

2 - we convert the arrayList to HashSet

3 - then we put the stringSet and apply

4 - you getStringSet within HashSet and recreate ArrayList to set the HashSet.

public class MainActivity extends AppCompatActivity {
    ArrayList arrayList = new ArrayList<>();

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

        SharedPreferences prefs = this.getSharedPreferences("com.example.nec.myapplication", Context.MODE_PRIVATE);

        HashSet set = new HashSet(arrayList);
        prefs.edit().putStringSet("names", set).apply();


        set = (HashSet) prefs.getStringSet("names", null);
        arrayList = new ArrayList(set);

        Log.i("array list", arrayList.toString());
    }
}