public int islandPerimeter(int[][] grid) {
if (grid == null || grid.length == 0) {
int m = grid.length, n = grid[0].length;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (i == 0 || grid[i - 1][j] == 0) edges += 1;
if (i == m - 1 || grid[i + 1][j] == 0) edges += 1;
if (j == 0 || grid[i][j - 1] == 0) edges += 1;
if (j == n - 1 || grid[i][j + 1] == 0) edges += 1;