JDK源码阅读-------自学笔记(十四)(java.util.Calendar日历类)

Calendar

• 提供了关于日期计算的相关功能，比如：年、月、日、时、分、秒的展示和计算。
• GregorianCalendar 是 Calendar 的一个具体子类，提供了世界上大多数国家/地区使用的标准日历系统
• 所在包java.util.Calendar

实战

• 初始化

  1    Calendar calendar = new GregorianCalendar();

• 打印结果

  1         Calendar calendar = new GregorianCalendar(3000, 12, 12, 15, 31, 42);
  2
  3         System.out.println(calendar);

• 获取对象的值

   1         Calendar calendar = new GregorianCalendar(3000, 12, 12, 06, 31, 42);
   2
   3         StringBuilder stringBuilder = new StringBuilder();
   4
   5         stringBuilder.append(calendar.get(Calendar.YEAR));
   6         stringBuilder.append("-");
   7         stringBuilder.append(calendar.get(Calendar.MONTH));
   8         stringBuilder.append("-");
   9         stringBuilder.append(calendar.get(Calendar.DATE));
  10
  11         System.out.println(stringBuilder.toString());

注:
    参数表示 日：Calendar.DATE和Calendar.DAYOFMONTH同义 星期几：1-7.(周日是1，周一是2......周六是7)

• 设置日期

   1         Calendar calendar = new GregorianCalendar();
   2
   3         calendar.set(Calendar.YEAR,10000);
   4         calendar.set(Calendar.MONTH,10);
   5         calendar.set(Calendar.DATE,15);
   6
   7         StringBuilder stringBuilder = new StringBuilder();
   8
   9         stringBuilder.append(calendar.get(Calendar.YEAR));
  10         stringBuilder.append("-");
  11         stringBuilder.append(calendar.get(Calendar.MONTH));
  12         stringBuilder.append("-");
  13         stringBuilder.append(calendar.get(Calendar.DATE));
  14
  15         System.out.println(stringBuilder.toString());

• 日期的计算

   1         Calendar calendar = new GregorianCalendar();
   2
   3         // 往后300天后的日期
   4         calendar.add(Calendar.DATE,300);
   5
   6
   7         StringBuilder stringBuilder = new StringBuilder();
   8
   9         stringBuilder.append(calendar.get(Calendar.YEAR));
  10         stringBuilder.append("-");
  11         stringBuilder.append(calendar.get(Calendar.MONTH));
  12         stringBuilder.append("-");
  13         stringBuilder.append(calendar.get(Calendar.DATE));
  14
  15         System.out.println(stringBuilder.toString());

• 日期对象和时间对象的转化

   1 public static void main(String[] args) throws ParseException {
   2
   3         Calendar calendar = new GregorianCalendar();
   4
   5         Date date = calendar.getTime();
   6         System.out.println("日历转日期:"+"\n"+date);
   7
   8         Calendar calendar1 = new GregorianCalendar();
   9         calendar1.setTime(new Date());
  10
  11         System.out.println("日期转日历:");
  12         printYearAndMonthAndDay(calendar1);
  13
  14     }
  15
  16     private static void printYearAndMonthAndDay(Calendar calendar) {
  17         StringBuilder stringBuilder = new StringBuilder();
  18
  19         stringBuilder.append(calendar.get(Calendar.YEAR));
  20         stringBuilder.append("-");
  21         stringBuilder.append(calendar.get(Calendar.MONTH));
  22         stringBuilder.append("-");
  23         stringBuilder.append(calendar.get(Calendar.DATE));
  24
  25         System.out.println(stringBuilder.toString());
  26     }

• 编写程序，利用GregorianCalendar类，打印当前月份的日历，今天的日期是 2017-05-18

样式:

代码:

  1     public static void main(String[] args) {
  2
  3         //输入日期处理
  4         String printClientDate = getPrintClientDate();
  5
  6         try {
  7             // 日期格式化
  8             Calendar c = getFormatCalendar(printClientDate);
  9
 10             //获取月份中的哪一天
 11             int day = c.get(Calendar.DAY_OF_MONTH);
 12
 13             // 获取日期最大值
 14             int days = c.getActualMaximum(Calendar.DATE);
 15
 16             //第一行周数空格的打印
 17             getWeekResult(c);
 18
 19             //输出月份内日期
 20             getDateResult(c, day, days);
 21
 22         } catch (ParseException e) {
 23             e.printStackTrace();
 24         }
 25     }
 26
 27     /**
 28      * 获取日期返回结果
 29      *
 30      * @param c    输入日期对像
 31      * @param day  当前输入的天数
 32      * @param days 输入的月最多多少天
 33      */
 34     private static void getDateResult(Calendar c, int day, int days) {
 35
 36         for (int i = 1; i <= days; i++) {
 37
 38             // 打印的天数是否是当前输入的天数,是加*,不是直接打印
 39             if (day == c.get(Calendar.DAY_OF_MONTH)) {
 40                 //标记输入的天数(即当前输入天)
 41                 System.out.print(c.get(Calendar.DAY_OF_MONTH) + "*\t");
 42             } else {
 43                 System.out.print(c.get(Calendar.DAY_OF_MONTH) + "\t");
 44             }
 45
 46             // 获取当前日期是周几,如果是周六,就进行换行
 47             if (c.get(Calendar.DAY_OF_WEEK) == Calendar.SATURDAY) {
 48                 System.out.println();
 49             }
 50
 51             //每次打印完,下次打印前,天数加一天
 52             c.add(Calendar.DAY_OF_MONTH, 1);
 53
 54         }
 55     }
 56
 57     /**
 58      * 获取输入周
 59      *
 60      * @param c 输入日期
 61      */
 62     private static void getWeekResult(Calendar c) {
 63         System.out.println("日\t一\t二\t三\t四\t五\t六");
 64
 65         // 当前日期置为1,就是日历的第一天
 66         c.set(Calendar.DAY_OF_MONTH, 1);
 67
 68         // 第一行日历根据周几,前边添加几个换行符
 69         for (int i = 0; i < c.get(Calendar.DAY_OF_WEEK) - 1; i++) {
 70             System.out.print("\t");
 71         }
 72     }
 73
 74     /**
 75      * 获取日期格式化后
 76      *
 77      * @param printClientDate 输入的日期
 78      * @return 返回日期对象
 79      * @throws ParseException 产生异常
 80      */
 81     private static Calendar getFormatCalendar(String printClientDate) throws ParseException {
 82         Date date;
 83         DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
 84         date = df.parse(printClientDate);
 85         Calendar c = new GregorianCalendar();
 86         c.setTime(date);
 87
 88         System.out.println("您刚刚输入的日期是:" + df.format(date));
 89         return c;
 90     }
 91
 92     /**
 93      * 获取控制台输入日期
 94      *
 95      * @return 输入的日期
 96      */
 97     private static String getPrintClientDate() {
 98         System.out.println("请输入日期(格式为:2020-9-10):");
 99         Scanner scanner = new Scanner(System.in);
100         return scanner.nextLine();
101     }

注:

JDK8,已经推出了新的取代的新方案,

详情查阅 https://www.cnblogs.com/liuyangfirst/p/11257602.html