Array 3d problem

[tnrh1]

Hello everyone,
I have an 2d array that represent a tic tac toe board.
And empty box is just "" ;
My current game board is saved in ar1 which is 2d string array.
I want to make an array of game boards which is array of 2d array = 3d array.
So I guess it would be like that:

String[][][]ar3 = new String[80][9][9]; // array of game boards
		
			for(int k=0;k<ar3.length;k++)// filling the array with the current game board
			{
				ar3[k] = ar1;
			}

Yea I want 80 boards and the game would be 9x9.
Till now everything is fine .. but now I would like to look on the game board(ar1) and make every possible move on the ar3.
So for every possible move I got a board on ar3.
For that I would create an array that would contain the empty indexes on the board which is every possible move on ar2:

int[][]ar2 = new int[81][2]; // contains blank boxes indexes
			int line = 0;
			
			for(int k=0;k<SIZE;k++) //finds blank boxes indexes and adding to the array
				for(int j=0;j<SIZE;j++,line++)
				{
					if(ar1[k][j].equals(""))
					{
						ar2[line][0] = k;
						ar2[line][1] = j;
					}
					else
					{
						ar2[line][0] = -1;
						ar2[line][1] = -1;
					}
					
				}

As you can see in case that the box has something else then "" which is X or O then I put -1
This code is doing what I want but here comes the problem now I will try to generate all the possible moves which stored in ar2 in ar3:

String[][][]ar3 = new String[80][9][9]; // array of game boards
			
			for(int k=0;k<ar3.length;k++)// filling the array with the current game board
			{
				ar3[k] = ar1;
			}
			for(int k=0;k<ar3.length;k++)// making a move
			{
				int i1 = ar2[k][0];
				int i2 = ar2[k][1];
				if(!(i1 == -1 || i2 == -1))
					if(num%2==0)
						ar3[k][i1][i2] = "X";
					else
						ar3[k][i1][i2] = "O";
			}

I have no idea why instead of making a single move for each board , for each index in ar3 it's making all of the moves for all of the boards .. for example (I will demonstrate on a 3x3 board)
^ means empty
The board before looks like this:

^ ^ ^
^ X ^
^ ^ ^
but after the "move" i'm trying to make (let's say 0,0)
all of the boards looks like this:

O ^ ^
^ X ^
^ ^ ^

Instead just of the first 1... and then I'm doing the same thing with diffrent indexes for the second board (ar3[1]) but it affects all of the boards.. (ar3[0-k]) so eventually I got 80 boards which are the same.
Any one got an idea?
Why it changes all of the boards?instead just the one on the K index?

Thanks!

[Sierra]

What I suspect is a common error of confusing immutable and mutable types:
ar3[k] = ar1;

You assign a field to the ar3 - take a look at your board after the change - ar1 is changed and all of the ar3 will be too because they actually reference it!
You need to copy every single cell by itself. What you want is a method:

	public static void copyarray(String[][] sArrayDest, String[][] sArraySrc)
	{
		for (int i=0; i<sArraySrc.length; i++)
		for (int t=0; t<sArraySrc[i].length; t++)
		{
			sArrayDest[i][t]	= sArraySrc[i][t];
		}
	}

[tnrh1]

Thank you so much!