java之Calendar类

Posted 2020-11-19 jiangjunwei

 1 public class Demo9_Calendar {
 2 
 3     /*
 4      * A:Calendar是一个抽象类
 5      * B：成员方法
 6      *    public static Calendar getInstance()    
 7      *    public int get(int field)
 8      * C:成员方法
 9      *    public void add(int field, int amount)    对指定的字段进行向前或向后加或减
10      *    public final void set(int year, int month, int date)   对指定字段进行修改
11      */
12     public static void main(String[] args) {
13 
14         //demo1();
15         Calendar c = Calendar.getInstance();
16         c.add(Calendar.MONTH, -1);                   //月份减1
17         c.set(Calendar.YEAR, 2088);                  //年份修改为2088
18         System.out.println(c.get(Calendar.YEAR) + "年" + getNum(c.get(Calendar.MONTH) + 1) + "月" 
19                 + getNum(c.get(Calendar.DAY_OF_MONTH)) + "日" + getWeek(c.get(Calendar.DAY_OF_WEEK)));
20         
21         
22     }
23 
24     public static void demo1() {
25         Calendar c = Calendar.getInstance();     //相当于父类引用指向子类对象
26         System.out.println(c.get(Calendar.YEAR));
27         System.out.println(c.get(Calendar.MONTH)); //月份是从0开始的
28         System.out.println(c.get(Calendar.DAY_OF_MONTH));
29         System.out.println(c.get(Calendar.DAY_OF_WEEK)); //周日是第一天
30         System.out.println(c.get(Calendar.YEAR) + "年" + getNum(c.get(Calendar.MONTH) + 1) + "月" 
31                 + getNum(c.get(Calendar.DAY_OF_MONTH)) + "日" + getWeek(c.get(Calendar.DAY_OF_WEEK)));
32     }
33 
34     /**
35      * 将星期存储表中进行查表
36      * @param week
37      * @return 
38      */
39     public static String getWeek(int week) {
40         String[] arr = {"","星期日","星期一","星期二","星期三","星期四","星期五","星期六"};
41         return arr[week];
42     }
43     
44     /**
45      * @param num
46      * @return String
47      */
48     public static String getNum(int num) {
49         /*if (num < 10) {
50             return "0" + num;
51         }else {
52             return "" + num;
53         }*/
54         return num > 9 ? "" + num : "0" + num;
55     }
56 }

利用Calendar类计算某一年是否是闰年：

 1 /*
 2      * 给定一个年份，判断是否是闰年
 3      * 1.提示键盘输入年份
 4      * 2.创建Calendar对象
 5      * 3.通过set方法将日期设置为哪一年的3月1日
 6      * 4.将日减1
 7      * 5.判断日是否是29，得到结果
 8      */
 9     public static void main(String[] args) {
10 
11         Scanner sc = new Scanner(System.in);
12         System.out.println("请输入需要判断的年份：");
13 //        int year = sc.nextInt();
14 //        System.out.println(getYear(year));
15         
16         //优化，判断输入是否是4位数字字符串
17         int year = 0;
18         String s = sc.nextLine();
19         String regex = "\d{4}";
20         if (s.matches(regex)) {
21             year = Integer.parseInt(s);
22             System.out.println(getYear(year));
23             
24         }else {
25             System.out.println("输入有误！");
26         }
27         
28     }
29     
30     public static boolean getYear(int year) {
31         Calendar c = Calendar.getInstance();
32         c.set(year, 2, 1);
33         c.add(Calendar.DAY_OF_MONTH, -1);
34         System.out.println(c.get(Calendar.DAY_OF_MONTH));
35         return c.get(Calendar.DAY_OF_MONTH) == 29;
36     }