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So I have a 2D character array that I am working with. Each space may either be occupied by a 'C', 'M', or 'N'(meaning not important). I have two methods, one that checks 4 spaces around an element, and one that checks 8 spaces around an element. Here is the former. 

public boolean checkAnySpace4(char[][] grid, int x, int y)
    {
        if(grid[x-1][y] == 'N' || grid[x-1][y] == 'M'|| grid[x-1][y] == 'C')
        {
            return false;
        }
        if(grid[x-1][y-1]  == 'N' || grid[x-1][y-1]  == 'M'|| grid[x][y-1]  == 'C')
        {
            return false;
        }
        if(grid[x][y-1]  == 'N' || grid[x][y-1]  == 'M'|| grid[x][y-1]  == 'C')
        {
            return false;
        }
        if(grid[x+1][y]  == 'N' || grid[x+1][y]  == 'M'|| grid[x+1][y]  == 'C')
        {
            return false;
        }
        else 
            return true;
    }

I simply want the method to return false if any of the surrounding elements(whether 4 or 8) are already occupied, or true if all are open. How would I do this so that I don't get an IndexOutOfBounds error?

Edit: Here is the rest of the code.

public void start(int steps)
    {
        char [][] grid = new char[25][25];


        int numCells = 0;
        while (numCells < 10) {

            //System.out.println("step = " + i);
            int random = (int)   Math.floor((Math.random() * 24));
            int random2 = (int)  Math.floor((Math.random() * 24));

            if(checkGrid(grid, random, random2) == true) //if current cell is empty
            {
                addCellToGrid(grid, random, random2, 'N');//add cell with different coordinates
                numCells++;
            }
        }

        printGrid(grid);

        System.out.print("exiting before steps");
        //System.exit(-1);
        /*
         * Fix array index out of bounds error
         * 
         */



        for(int i = 0; i < steps; i++)//populate array
        {



            for(int j = 0; j < 25; j++)
            {
                for(int k = 0; k < 25; k++)
                {
                    if(new Random().nextDouble() <= (1-e)) //probability that cell dies
                    {
                        die(grid, j, k);
                        continue;
                    }

                    else ////if not dead, mutate with prob p_n for N,M cells, p_c for C cells
                    {
                        if(new Random().nextDouble() <= m) //mutate with prob m
                        {
                            mutate(grid, j,k);//mutate cell

                                if(grid[j][k] == 'N' || grid[j][k] == 'M')//if cell is type N or M
                                {
                                    if(checkAnySpace4(grid, j, k))//if cell has space to divide
                                    {
                                        if(new Random().nextDouble() <= p_n)//divide with probability p_n
                                        {
                                            divide(grid, j, k);//divide cell
                                        }
                                    }
                                    else
                                    {
                                        continue; //cell does not divide, do nothing
                                    }
                                }
                            }
                             if(grid[j][k] == 'C')//C grid[j][k]s cannot mutate
                            {
                                if(checkAnySpace8(grid, j, k))//if cell has space to divide
                                {
                                    if(new Random().nextDouble() <= p_c)//divide with probability p_c
                                    {
                                        divide(grid, j, k);//divide cell
                                    }
                                }
                            }   
                        }    
                }           
            }
        }    

    printGrid(grid);    
    }

The error is thrown at the first if statement of the checkAnySpace4 method.

Kyle Weise
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  • The code you have shown does not have any error checking to verify that the x,y values passed to the method are within range of valid indices currently in grid[][]. You may want to do some error checking in this method and maybe show us the code where you are calling the method and how grid[][] is getting populated. – pczeus Feb 21 '16 at 01:41
  • I have edited the post to contain the rest of the relevant code. – Kyle Weise Feb 21 '16 at 01:57

1 Answers1

0

add two more variables to the function: size_x and size_y to your function.

then:

public boolean checkAnySpace4(char[][] grid, int x, int y, int size_x, int size_y)
{
    if(x == 0 || y == 0 || x == size_x || y == size_y){
        /*complain on the console or raise an exception*/
        return false;
    }

    if(grid[x-1][y] == 'N' || grid[x-1][y] == 'M'|| grid[x-1][y] == 'C')
    {
        return false;
    }
    if(grid[x-1][y-1]  == 'N' || grid[x-1][y-1]  == 'M'|| grid[x][y-1]  == 'C')
    {
        return false;
    }
    if(grid[x][y-1]  == 'N' || grid[x][y-1]  == 'M'|| grid[x][y-1]  == 'C')
    {
        return false;
    }
    if(grid[x+1][y]  == 'N' || grid[x+1][y]  == 'M'|| grid[x+1][y]  == 'C')
    {
        return false;
    }
    else 
        return true;
}

you might have to subtract 1 from size_x and size_y.

SIGSTACKFAULT
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