Question

I’m making a game tree for a tic tac toe.

I have a method called buildGameTree which gets a TreeNode (the treeNode has an array of 80 childrens) and it calculates every kind of possible move. Each move is a 1 children of course.

Here is the error I get:

Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at Main.buildGameTree(Main.java:169)
at Main.buildGameTree(Main.java:218)
at Main.buildGameTree(Main.java:218)
...
at Main.buildGameTree(Main.java:218)

And here is my code:

private void buildGameTree(TreeNode t1)
        {
            String[][] ar1 = (String[][]) t1.getData(); //ar1 is a game board
            
            if(!gameOver(t1)) 
            {
                //printTree(t1);
                int[][]ar2 = new int[81][2];
                int line = 0;
                
                for(int k=0;k<SIZE;k++) //looking for ""
                    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;
                        }
                        
                    }
                
                String[][][]ar3 = new String[80][9][9]; // array of game boards
                
                for(int k=0;k<ar3.length;k++)// filling the array.. ar1 is a 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";
                }
                
                TreeNode<String[][]>[] ar4 = new TreeNode[80]; 
                
                for(int k=0;k<ar3.length;k++)
                {
                    ar4[k] = new TreeNode<String[][]>(ar3[k]);
                }
                t1.setChildren(ar4);
                
                for(int k=0;k<ar4.length;k++)
                {
                    buildGameTree(ar4[k]);
                }
            }
        }

Sorry for putting so much code lines but it’s the only way to show my problem.

Line 169 is: if(!gameOver(t1))

Line 218 is: buildGameTree(ar4[k]);

Maybe my tree is to big to be saved in the memory?

btw the game board is an array of 9×9, empty block is "", and you have "X" and "O" of course.
ar2 is kind of a table of indexes which will be the next moves in the game.

EDIT

public boolean gameOver(TreeNode t1)
        {
            String[][] ar1 = (String[][]) t1.getData();
            for(int k=0;k<ar1.length;k++)
            {
                for(int j=0;j<ar1.length;j++)
                    if(ar1[k][j].equals(""))
                        return false;
            }
            return true;
        }

EDIT
I added some print lines n stuff to find what is causing the error and I found out that the first board is fine and then something wierd happens:
In the print function I change the "" to "^" so we could see the board

^^^^^^^^^
^^^^^^^^^
^^^^^^^^^
^^^^^^^^^
^^^^^^^^^
^^^^^^^^^
^^^^^^^^X
^^^^^^^^^
^^^^^^^^^

OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOX
OOOOOOOOO
OOOOOOOO^

OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOO
OOOOOOOOX
OOOOOOOOO
OOOOOOOO^

As you can see it’s making many moves instead of 1 since almost the whole board is covered by "O" and then it’s stays the same that’s the reason I get the overflow exception.
What is wrong with my code?
That’s must to be over here:

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";
                }

As I said ar3 is an array of game boards or game options.. for each ar3[k] I make a diffrent move only if it’s not equals to -1 the block content (means there is something into it X or O).

EDIT
Since I got an answer why it’s overflowing I will close this question and open another one regarding to my new problem thanks.

Answer 1

THe problem you have is that your coude is a infinite loop.

The argument you passs to internal call of buildGameTree(TreeNode) (line 218) do not return false from gameOver(TreeNode). There fore your code in each step create the tree.