Java字符串替换问题

Question

I have a code in which I am using replace method on Java String, but it is not working.. Please point out the mistake..

static String[] cavityMap(String[] grid) {
    String[] ans = grid;
    for(int i = 1; i<= grid.length-2; i++){
        for(int j = 1; j<= grid[i].length()-2; j++){
            int e = Integer.parseInt(grid[i].charAt(j) + "");
            int t = Integer.parseInt(grid[i - 1].charAt(j) + "");
            int b = Integer.parseInt(grid[i + 1].charAt(j) + "");
            int l = Integer.parseInt(grid[i].charAt(j - 1) + "");
            int r = Integer.parseInt(grid[i].charAt(j + 1) + "");
        if(e > t && e > b && e > l && e > r){
            ans[i] = ans[i].replace("X",(ans[i].charAt(j) + ""));
            System.out.println(ans[i].replace("X",(ans[i].charAt(j) + "")));
        }
        }    
   }    
   return ans;
}

The code execution is going in if conditional part.. But it is printing the same value as before.. Why is it not replacing the String with "X".. Thanks in advance

Answer 1

ans[i].replace("X",(ans[i].charAt(j) + ""))

will replace all occurences of "X" with ans[i].charAt(j) + "" .

If your intention is to replace ans[i].charAt(j) + "" with "X" you will need to swap your params:

ans[i].replace((ans[i].charAt(j) + ""), "X")

Also, using concatenation with empty string to cause conversion from char to String is discouraged. Consider explicitly invoking Character.toString or String.valueOf

ans[i].replace(String.valueOf(ans[i].charAt(j)), "X")

or better yet, since your replacement is a single char , just work in that type

ans[i].replace(ans[i].charAt(j), 'X')