```
public int islandPerimeter(int[][] grid) {
int perimeter = 0;
for (int i=0; i<grid.length; i++) {
for (int j=0; j<grid[i].length; j++) {
if(grid[i][j]==1) {
perimeter += 4;
if (i>0 && grid[i-1][j]==1)
perimeter -= 2;
if (j>0 && grid[i][j-1]==1)
perimeter -= 2;
}
}
}
return perimeter;
}
```