转圈打印矩阵

  /**
     * 转圈打印矩阵
     */
    public static void printMatrix(int[][] arr) {
        int a = 0;//（a.b）位置
        int b = 0;
        int c = arr[0].length - 1;（c，d）位置
        int d = arr.length - 1;
        while (a <c && b < d) {
            printEdge(arr, a++, b++, c--, d--);
        }
    }

private static void printEdge(int[][] arr, int a, int b, int c, int d) {
    for (int i = a; i <= c; i++) {
        System.out.print(arr[b][i] + " ");
    }
    for (int i = b+1; i <= d; i++) {
        System.out.print(arr[i][c] + " ");
    }
    for (int i = c - 1; i >= a; i--) {
        System.out.print(arr[d][i] + " ");
    }
    for (int i = d - 1; i > b; i--) {
        System.out.print(arr[i][a] + " ");
    }
}