public class Solution {    public void rotate(int[][] matrix) {        int n=matrix.length;        for (int i=0; i<n/2; i++) {            for (int j=i; j<n-1-i; j++) {                int tmp = matrix[i][j];                matrix[i][j] = matrix[n-1-j][i];                matrix[n-1-j][i] = matrix[n-1-i][n-1-j];                matrix[n-1-i][n-1-j] = matrix[j][n-1-i];                matrix[j][n-1-i] = tmp;            }        }    }}