rotate-matrix.java

public class Rotate {

    public static int[][] rotateImage(int[][] a) {
        final int len = a.length;
        println("LEN: " + len / 2);
        println("========");
        for (int s = 0; s < len / 2; s++) {
            println("S: " + s);
            for (int i = 0; i < len - 2 * s - 1; i++) {

                int temp = a[s][s + i];
                println(String.format("temp = a[%s][%s]", s, s + i));

                a[s][s + i] = a[len - s - i - 1][s];
                printD(s, s + i, len - s - i - 1, s, a[s][s + i], a[len - s - i - 1][s]);

                a[len - s - i - 1][s] = a[len - s - 1][len - s - i - 1];
                printD(len - s - i - 1, s, len - s - 1, len - s - i - 1, a[len - s - i - 1][s], a[len - s - 1][len - s - i - 1]);

                a[len - s - 1][len - s - i - 1] = a[s + i][len - s - 1];
                printD(len - s - 1, len - s - i - 1, s + i, len - s - 1, a[len - s - 1][len - s - i - 1], a[s + i][len - s - 1]);

                a[s + i][len - s - 1] = temp;
                println(String.format("a[%s][%s] = temp\n%s = %s", s + 1, len - s - 1, a[s + i][len - s - 1], temp));

                print(a);
                println("========");
            }
            println("========");
        }

        return a;
    }

    private static void printD(int y1, int x1, int y2, int x2, int c, int d) {
        println(String.format("a[%s][%s] = a[%s][%s]\n%s = %s\n", y1, x1, y2, x2, c, d));
    }

    private static void println(String m) {
        System.out.println(m);
    }

    private static void print(int[][] a) {
        for (int[] y: a) {
            for (int x: y) {
                System.out.print(x + " ");
            }
            System.out.print("\n");
        }
        System.out.print("\n");
    }

}

just to understand matrix rotation