01_程序流程控制

class Nine_NineTable  
{
    public static void main(String[] args) 
    {
        for (int i = 1;i <=9 ;i++ )
        {
            for(int j = 1; j <= i ;j++)
            {
                System.out.print(i + "*" + j + "=" + (i*j) + "\t");
            }
            System.out.println();
        }
    }
}

一/九九乘法表:使用for循环结构

二/switch-case分支结构：编写程序：从键盘上输入第n年的“month”和“day”，要求通过程序 输出输入的日期为第n年的第几天。

 1 //使用switch-case结构
 2 import java.util.Scanner;
 3 class SwitchTest 
 4 {
 5     public static void main(String[] args) 
 6     {
 7         Scanner scan = new Scanner(System.in);
 8         System.out.println("请输入年份：");
 9         int year = scan.nextInt();
10         System.out.println("请输入月份：");
11         int month = scan.nextInt();
12         System.out.println("请输入当月的第几天：");
13         int day = scan.nextInt();
14         int sumDays = 0;
15         switch (month)
16         {
17         case 12://月份倒着写，使用break结束
18             sumDays += 30;
19         case 11:
20             sumDays += 31;
21         case 10:
22             sumDays += 30;
23         case 9:
24             sumDays += 31;
25         case 8:
26             sumDays += 31;
27         case 7:
28             sumDays += 30;
29         case 6:
30             sumDays += 31;
31         case 5:
32             sumDays += 30;
33         case 4:
34             sumDays += 31;
35         case 3://判断是不是闰年
36             if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) 
37             {
38                 sumDays += 29;//闰年29天
39             } 
40             else 
41             {
42                 sumDays += 28;//平年28天
43             }
44         case 2:
45             sumDays += 31;   
46         case 1:
47             sumDays += 0;
48             break;
49         }
50         sumDays += day;//加上输入的当月天数
51         System.out.println("这是" + year + "年" + month + "月" + day + "日是当年的第" + sumDays +"天");
52     }
53 }