Deep cloning an object of a class in java

Question

I have an object game of my Game.java class in my main class. I need to create a copy (game_copy) of game object such that when I make changes to the board of game_copy, the board of game does not get changed. I make this game_copy object as:

Game game_copy = new Game() ;
game_copy = game.clone() ;

But still when I make changes to the board of game_copy, the board of game gets changed as they still share a reference. How do I sort out this problem? Here are my Game and rplayer classes that I am using:

class Game implements Cloneable{
     int n;
     ArrayList<ArrayList<String>> board;
     rplayer [] players;
     int a ;

    public Game(int n){
      this.n=n;
      players = new rplayer[2] ;
      players[0]=new rplayer(this.a);
      players[1]=new rplayer(this.a);
      board= new ArrayList<ArrayList<String>>();
       for(int p= 0 ; p < n*n ; p++){
        ArrayList<String> r = new ArrayList<String>() ;
        board.add(r) ;
       }
     }

   public Game clone(){ 
    Game gm ;
    try { 
        gm =  (Game) super.clone(); 
    } 
    catch (CloneNotSupportedException e) { 
        System.out.println (" Cloning not allowed. " );
         return null; 
    }
    return gm
 }
}

class rplayer{
    int a;
    public rplayer(int a){
      this.a=a;
    }
}

This is what I tried before trying to use .clone() method, but the idea of making a copy constructor didn't work either. Both the objects were always related.

public Game(Game g){
this.n=g.n;
this.players = new rplayer[2] ;
rplayer[] temp_players = new rplayer[2] ;
temp_players = g.players;
this.players = temp_players ;
this.board= new ArrayList<ArrayList<String>>();
ArrayList<ArrayList<String>> temp_board = new ArrayList<ArrayList<String>>() ;
    for(int p= 0 ; p < n*n ; p++){
        ArrayList<String> r = new ArrayList<String>() ;
        board.add(r) ;
        temp_board.add(r) ;
    }
    temp_board = g.board ;
    board= temp_board;
}

Answer 1

Per the Javadocs:

Otherwise, this method creates a new instance of the class of this object and initializes all its fields with exactly the contents of the corresponding fields of this object, as if by assignment; the contents of the fields are not themselves cloned. Thus, this method performs a "shallow copy" of this object, not a "deep copy" operation.

In other words, a new object IS created, but the references inside the object still point to the same member variables. You need to make copies of the contents inside the object as well as the object itself.

https://docs.oracle.com/javase/7/docs/api/java/lang/Object.html