Rotate Matrix 90 degrees

I had an elder post at http://mashijie.blogspot.ca/2015/06/rotating-nxn-matrix-90-degrees.html.
That is not as concise as this solution:
in order to rotate, flip it Diagonally, then vertically.

What to learn: diagonally swapping.

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public class Solution { void swap(int[][] matrix,int x, int y,int x1,int y1){ /* a=a^b; b=a^b; a=a^b;*/ int tmp = matrix[x][y]; matrix[x][y]=matrix[x1][y1]; matrix[x1][y1]=tmp; } public void rotate(int[][] matrix) { int len = matrix[0].length; //flip Diagonally for(int i =0; i<len-1; i++) { for(int j=0;j<len-i;j++) { swap(matrix,i,j, len-1-j,len-1-i); } } //vertically for(int i =0; i<len/2; i++) { for(int j=0;j<len;j++){ swap(matrix,i,j, len-i-1,j); } } } }