CODEWITHSUNDEEP
javaarraysindexoutofboundsexception
Sam Chuks
Sam Chuks

Reputation: 39

Game Of Life - Out Of Bounds array index

I'm working on the standard Game Of Life program for my Intro to Java course, and so far I've been able to accomplish a lot of it on my own. However, I'm having some difficulty with counting the neighbors of a given cell, to determine whether it lives or dies.

Here is my countNeighbors method:

public static int countNeighbors(int [][] board, int A, int B) 
{
    int [][]a = board;
    int count = 0;

    if (a[A][B] == 0 || a[A][B] == 1) {
        try{
            if (a[A-1][B-1] == 1) {count++;}
            if (a[A  ][B-1] == 1) {count++;}
            if (a[A+1][B-1] == 1) {count++;}
            if (a[A-1][B  ] == 1) {count++;}
            if (a[A+1][B  ] == 1) {count++;}
            if (a[A-1][B+1] == 1) {count++;}
            if (a[A  ][B+1] == 1) {count++;}
            if (a[A+1][B+1] == 1) {count++;} 
        }

    catch (ArrayIndexOutOfBoundsException e) {}

    }
    return count;
}

When I run my program, this method does not count the neighbors correctly, thus initializing an incorrect new generation. How do I overcome the out of bounds indices of an array?

Upvotes: 0

Views: 217

Answers (1)

Eran
Eran

Reputation: 393986

You should check that A and B fall within the bounds of the board array. Then you should check that adding or subtracting 1 to A or B keeps you within the bounds of the array.

For example:

if (A < a.length && B < a[A].length) {
    if (a[A][B] == 0 || a[A][B] == 1) {
        if (A > 0 && B > 0)
            if (a[A-1][B-1] == 1) {count++;}
        ....
        if (A+1 < a.length && B+1 < a[A].length)
            if (a[A+1][B+1] == 1) {count++;} 
    }
}

Upvotes: 1

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