整体思路：

代码设计：

代码呈现：

class Solution {int m,n,ret;boolean[][] vis;public int numIslands(char[][] grid) {m = grid.length;n = grid[0].length;vis = new boolean[m][n];for(int i = 0; i < m; i++)for(int j = 0; j < n; j++){if(!vis[i][j] && grid[i][j] == '1'){ret++;//把这个岛屿附近的1标记一下dfs(grid,i,j);}}return ret;    }int[] dx = {0,0,-1,1};int[] dy = {1,-1,0,0};private void dfs(char[][] grid, int i, int j){vis[i][j] = true;//标记for(int k = 0; k < 4; k++){int x = i + dx[k]; int y = j + dy[k];if(x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] && grid[x][y] == '1'){dfs(grid,x,y);}}}
}