RotateImage.java

class RotateImage {
    public void rotate(int[][] matrix) {
        
        /*
         * clockwise rotate
         * first reverse up to down, then swap the symmetry 
         * 1 2 3     7 8 9     7 4 1
         * 4 5 6  => 4 5 6  => 8 5 2
         * 7 8 9     1 2 3     9 6 3
        */

        int s = 0,                  
            e = matrix.length - 1;
        
        while(s < e){                    //Swap the Full rows ie 1st and Last row
            int[] temp = matrix[s];
            matrix[s] = matrix[e];
            matrix[e] = temp;
            s++; 
            e--;
        }
        
        //Now Just swap the symmetry
        for(int i = 0; i < matrix.length; i++){
            for(int j = i+1; j < matrix[i].length; j++){
                
                int temp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = temp;
            }
        }
    }
}