winInColumn方法应该可以，但是不能。 为什么？

Question

I have this method for a connect 4 game so that you can win in a column. However I get an Index Array out of bounds exception -1. The array it goes through is 8x8 in size (private int [][] values = new int [8][8];).

Where have i gone wrong?

public int winInAColumn(){
    int sum; //set sum as an integer
    for(int j=0;j<8;j++){ //loop through the rows
        for(int i=4;i>-1;i--){ //loop through columns. I must equal 4 as there must be three disks next to  
            sum = 0; //set sum to 0
            for(int k=i;k>i-4;k--){ //loop backwards through k while k is bigger than i minus 4
                sum+=values[k][j]; //sum + sum = the value in  i and j
            }
            if(Math.abs(sum)==4){
                if(sum/4 == 1){
                    if(JOptionPane.showConfirmDialog(null, "Blue Has Won", "Game over", JOptionPane.OK_CANCEL_OPTION) == 0){
                        //
                    }
                    else 
                    {
                        System.exit(0);
                    } 
                }

                else if (sum/4 == -1){
                    if(JOptionPane.showConfirmDialog(null, "Blue Has Won", "Game over", JOptionPane.OK_CANCEL_OPTION) == 0)
                    {
                        //
                    }
                    else
                    {
                        System.exit(0);
                    } 
                }
            }
        }
    }
                return 0;
        //JOptionPane.showMessageDialog(null, "No one won this time.");
}

Answer 1

In the second loop, i goes backward from 4 to 0, and in the third loop, k goes backward from i to i - 3, which can be as low as -3, hence the exception.

I did not really try to understand your algorithm in detail, but perhaps replace k>i-4 by k>i-4 && k>=0 would do the trick...