android - Create file of an ArrayList of java class -

i'm making android app reminds me when it's someone's birthday.

i'm able add name , corresponding date. but, i'm stuck @ saving part. i've tried looking solutions unable port needs. since it's arraylist , not simple string cannot serialized (if i'm correct?) , therefore not saved. there other way save kind of data?

here code:

item.java:

public class item implements serializable{   private string name;   private string date;    public item(string name, string date){       this.name = name;       this.date = date;   }    public string getname(){       return name;   }    public string getdate(){       return date;   }    public void setname(string name){       this.name = name;   }    public void setdate(string date){       this.date = date;   } } 

mainactivity.java:

public class mainactivity extends appcompatactivity {  recyclerview recyclerview; static recyclerviewadapter adapter;  static arraylist<item> itemlist = new arraylist<>();  private static string nametext; private static string birthstring;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);      setcontentview(r.layout.activity_main);      toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar);     setsupportactionbar(toolbar);      recyclerview = (recyclerview) findviewbyid(r.id.recyclerview);      linearlayoutmanager llm = new linearlayoutmanager(this);     llm.setorientation(linearlayoutmanager.vertical);      recyclerview.setlayoutmanager(llm);     recyclerview.setitemanimator(new defaultitemanimator());      adapter = new recyclerviewadapter(itemlist);     recyclerview.setadapter(adapter);      floatingactionbutton fab = (floatingactionbutton) findviewbyid(r.id.fab);     fab.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view view) {             addbirthday();         }     }); }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.menu_main, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); }  public static class datepickerfragment extends dialogfragment         implements datepickerdialog.ondatesetlistener {      @override     public dialog oncreatedialog(bundle savedinstancestate) {         // use current date default date in picker         final calendar c = calendar.getinstance();         int year = c.get(calendar.year);         int month = c.get(calendar.month);         int day = c.get(calendar.day_of_month);          // create new instance of datepickerdialog , return         return new datepickerdialog(getactivity(), this, year, month, day);     }      public void ondateset(datepicker view, int year, int month, int day) {         // date chosen user         month++;         birthstring = day + "-" + month + "-" + year;         itemlist.add(new item(nametext, birthstring));         adapter.notifydatasetchanged();         savearraylist(getcontext(), itemlist);     } }  private void addbirthday() {     alertdialog.builder builder = new alertdialog.builder(this);     builder.settitle("name");      final edittext input = new edittext(this);     input.setinputtype(inputtype.type_class_text);     builder.setview(input);     builder.setpositivebutton("ok", new dialoginterface.onclicklistener() {         @override         public void onclick(dialoginterface dialog, int which) {             nametext = input.gettext().tostring();              dialogfragment newfragment = new datepickerfragment();             newfragment.show(getsupportfragmentmanager(), "datepicker");         }     });     builder.setnegativebutton("cancel", new dialoginterface.onclicklistener() {         @override         public void onclick(dialoginterface dialog, int which) {             dialog.cancel();         }     });     builder.show(); }  public static void savearraylist(context c, arraylist<item> arraylist) {  }   } 

there's no problem serializing or deserializing arraylists in java:

    list<item> list = new arraylist<>();      list.add(new item("a", "2006"));     list.add(new item("b", "2016"));       // serialize     fileoutputstream fos = context.openfileoutput("list.ser", context.mode_private);     objectoutputstream os = new objectoutputstream(fos);     os.writeobject(list);     os.close();     fos.close();       // deserialize      fileinputstream filein = context.openfileinput("list.ser");     objectinputstream in = new objectinputstream(filein);     list = (list<item>) in.readobject();     in.close();     filein.close();      // implement tostring() in item     system.out.println(list);