Longest Line of Consecutive One in Matrix

https://leetcode.com/problems/longest-line-of-consecutive-one-in-matrix/description/

public class Solution {
    public int longestLine(int[][] M) {
        if(M == null || M.length == 0 || M[0] == null || M.length == 0){
            return 0;
        }

        int m = M.length, n = M[0].length;
        int[][][] dp = new int[m][n][4];
        int max = 0;

        for(int i = 0; i < m; i++){
            for(int j = 0; j < n; j++){
                if(M[i][j] == 0){
                    continue;
                }

                for(int k = 0; k < 4; k++){
                    dp[i][j][k] = 1;
                }

                if(inBound(i, j - 1, m, n)){
                    dp[i][j][0] = dp[i][j - 1][0] + 1;
                    max = Math.max(max, dp[i][j][0]);
                }

                if(inBound(i - 1, j - 1, m, n)){
                    dp[i][j][1] = dp[i - 1][j - 1][1] + 1;
                    max = Math.max(max, dp[i][j][1]);
                }

                if(inBound(i - 1, j, m, n)){
                    dp[i][j][2] = dp[i - 1][j][2] + 1;
                    max = Math.max(max, dp[i][j][2]);
                }

                if(inBound(i - 1, j + 1, m, n)){
                    dp[i][j][3] = dp[i - 1][j + 1][3] + 1;
                    max = Math.max(max, dp[i][j][3]);
                }

                max = Math.max(max, 1);
            }
        }

        return max;
    }

    private boolean inBound(int i , int j, int m, int n){
        return i >= 0 && i < m && j >= 0 && j < n;
    }
}