数据排序、九九乘法表、杨辉三角

        int[] nums = { 23, 12, 15, 9 };
        for (int i = 0; i < nums.length; i++) {
            int index = i;
            for (int j = i + 1; j < nums.length; j++) {
                if (nums[i] > nums[j]) {
                    index = j;
                }
            }
            System.out.println("第" + (i + 1) + "次排序前：");
            System.out.println(Arrays.toString(nums));

            int temp = nums[i];
            nums[i] = nums[index];
            nums[index] = temp;

            System.out.println("第" + (i + 1) + "次排序后：");
            System.out.println(Arrays.toString(nums));
        }

 1         int[] nums = { 23, 12, 15, 9 };
 2         for (int i = 0; i < nums.length; i++) {
 3             System.out.print("第" + (i + 1) + "次排序前：");
 4             System.out.println(Arrays.toString(nums));
 5 
 6             for (int j = 0; j < nums.length - i - 1; j++) {
 7                 if (nums[j] < nums[j + 1]) {
 8                     int temp = nums[j];
 9                     nums[j] = nums[j + 1];
10                     nums[j + 1] = temp;
11                 }
12             }
13 
14             System.out.print("第" + (i + 1) + "次排序后：");
15             System.out.println(Arrays.toString(nums));
16         }

1     public static void printChengfabiao(int i) {
2         for (int a = 1; a <= i; a++) {
3             for (int b = 1; b <= a; b++) {
4                 System.out.print(b + " * " + a + " = " + b * a + "\t");
5             }
6             System.out.println();
7         }
8     }

 1         int[][] nums = new int[8][];
 2         for (int i = 0; i <= nums.length - 1; i++) { // 控制轮数
 3             nums[i] = new int[i + 1]; // 开辟空间地址，循环给每个数组赋值，数组长度不固定
 4             for (int j = 0; j <= i; j++) {
 5                 if (i == 0 || j == 0 || j == i) {
 6                     nums[i][j] = 1;
 7                 } else {
 8                     nums[i][j] = nums[i - 1][j - 1] + nums[i - 1][j];
 9                 }
10                 System.out.print(nums[i][j] + "\t");
11             }
12             System.out.println();
13         }