CCI 1.6 旋转矩阵

给定一幅由N*N矩阵表示的图像，其中每个像素的大小为4字节，编写一个方法，将图像旋转90度。不占用额外内存空间能否做到？

package test;

public class RotateMatrix {

	public static void rotateMatrix(int[][] matrix){
		if(matrix==null || matrix.length==0 || matrix[0]==null || matrix[0].length==0)
			return;
		if(matrix.length != matrix[0].length)
			return;
		int n = matrix.length;
		for(int layer=0; layer < n/2; layer++){
			int first = layer;
			int last = n-layer-1;
			for(int i=first; i<last; i++){
				int offset = i-first;
				
				int temp = matrix[i][first];
				matrix[i][first] = matrix[last][i];
				matrix[last][i] = matrix[last-offset][last];
				matrix[last-offset][last] = matrix[first][last-offset];
				matrix[first][last-offset] = temp;
			}
		}
		
	}
	
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int[][] case1 = null;
		int[][] case2 = { {1,2,3}, {4,5,6}, {7,8,9} };
		
		int[][] testCase = case2;
		
		rotateMatrix(testCase);
		for(int i=0; i<testCase.length; i++){
			for(int j=0; j<testCase[0].length; j++){
				System.out.print(testCase[i][j]);
				System.out.print(" ");
			}
			System.out.println();
		}		
	}

}