CC1.6

public void rotate(int[][] matrix) {
		if(matrix == null)
			return;
		int N = matrix.length;
		for(int i = 0; i < N/2; i++)					// This is the layer
			for(int j = i; j < N-i-1; j++) {			// This is the offset to start
				// swap
				int t = matrix[i][j];
				matrix[i][j] = matrix[N-j-1][i];
				matrix[N-j-1][i] = matrix[N-i-1][N-j-1];
				matrix[N-i-1][N-j-1] = matrix[j][N-i-1];
				matrix[j][N-i-1] = t;
			}
	}