java - Parcel List of List of Parcelable object -

so i've parceled lists before, i'm trying parcel gameboard object, has list<list<tile>>. tile implements parcelable, i'm not sure how parcel list<list>. here's i've tried:

public class gameboard implements parcelable {     private string _id;     public string getid() { return _id; }     public void setid(string id) { _id = id; }      private list<list<tile>> _tiles;     public list<list<tile>> gettiles() { return _tiles; }     public void settiles(list<list<tile>> tiles) { _tiles = tiles; }      public gameboard(parcel in) {         _id = in.readstring();         in.readlist(_tiles, arraylist.class.getclassloader());     }      public gameboard() {      }      @override     public int describecontents() {         return 0;     }      @override     public void writetoparcel(parcel parcel, int i) {         parcel.writestring(_id);         parcel.writelist(_tiles);     }      public static final parcelable.creator<gameboard> creator = new parcelable.creator<gameboard>() {         public gameboard createfromparcel(parcel in) {             return new gameboard(in);         }          public gameboard[] newarray(int size) {             return new gameboard[size];         }     }; 

the tile class correctly implements parcelable, i'm not sure how read / write list<list>> when parceling class. ideas?

based on comments, extended arraylist class custom class , implemented parcelable:

public class tilelist extends arraylist<tile> implements parcelable {      public tilelist(){         super();     }      protected tilelist(parcel in) {         in.readtypedlist(this, tile.creator);     }      @override     public int describecontents() {         return 0;     }      @override     public void writetoparcel(parcel parcel, int i) {         parcel.writetypedlist(this);     }      public static final parcelable.creator<tilelist> creator = new parcelable.creator<tilelist>() {         public tilelist createfromparcel(parcel in) {             return new tilelist(in);         }          public tilelist[] newarray(int size) {             return new tilelist[size];         }     }; } 

and slight changes other class:

public class gameboard implements parcelable {     private string _id;     public string getid() { return _id; }     public void setid(string id) { _id = id; }      private list<tilelist> _tiles;     public list<tilelist> gettiles() { return _tiles; }     public void settiles(list<tilelist> tiles) { _tiles = tiles; }      public gameboard(parcel in) {         _id = in.readstring();         _tiles = new arraylist<>();         in.readtypedlist(_tiles, tilelist.creator);     }      public gameboard() {      }      @override     public int describecontents() {         return 0;     }      @override     public void writetoparcel(parcel parcel, int i) {         parcel.writestring(_id);         parcel.writetypedlist(_tiles);     }      public static final parcelable.creator<gameboard> creator = new parcelable.creator<gameboard>() {         public gameboard createfromparcel(parcel in) {             return new gameboard(in);         }          public gameboard[] newarray(int size) {             return new gameboard[size];         }     }; }