【日期-时间】Java中Calendar的使用

主要介绍了Calendar类的使用

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输出

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* 时间格式化
 * 当前时间：2016-12-02 16:46:27.079
 * 
 * 转换：String-->Date-->Calendar
 * 设置时间(方式1)：2014-08-01 09:18:34.123
 * 设置时间(方式2)：2016-12-01 19:08:54.123
 * 
 * ----YEAR-MONTH----
 * YEAR:2016
 * MONTH:11
 * ----Day-----
 * 本月第几天:1
 * 本周几:5
 * 今年的第 N天 :336
 * DAY_OF_WEEK_IN_MONTH:1
 * ----Hour-----
 * Hour:7
 * HOUR_OF_DAY:19
 * ----MINUTE-----
 * MINUTE:8
 * 
 * 向后推迟一个月(方式1)：2017-01-01 19:08:54.123
 * 向后推迟一个月(方式2)：2017-02-01 19:08:54.123
 * 向后推迟一小时(方式1)：2017-02-01 20:08:54.123
 * 向前推迟一小时(方式2)：2017-02-01 19:08:54.123
 * 设置为30分钟：2017-02-01 19:30:00.123
 * 
 * 开始时间：2014-12-15 16:46:27.116,毫秒数：1418633187116
 * 结束时间：2016-12-05 12:15:35.117,毫秒数：1480911335117
 * 相差天数：721
 * 
 * 本月最大天数：31

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程序

package com.sssppp.DateTime;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class CalendarExample {
   public static void main(String[] args) {
      Calendar cal = Calendar.getInstance();
      System.out.println("时间格式化");
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
      System.out.println("当前时间：" + sdf.format(cal.getTime()));
      System.out.println();
      
      try {
         System.out.println("转换：String-->Date-->Calendar");
         cal.setTime(sdf.parse("2014-8-1 9:18:34.123"));
         System.out.println("设置时间(方式1)：" + sdf.format(cal.getTime()));
      } catch (ParseException e) {
         e.printStackTrace();
      }
      
      //2016-12-01 19:08:54
      cal.set(2016, Calendar.DECEMBER, 1, 19, 8, 54);
      System.out.println("设置时间(方式2)：" +sdf.format(cal.getTime()));
      System.out.println();
      
      System.out.println("----YEAR-MONTH----");
      System.out.println("YEAR:" + cal.get(Calendar.YEAR));
      System.out.println("MONTH:" + cal.get(Calendar.MONTH));
      System.out.println("----Day-----");
      System.out.println("本月第几天:" + cal.get(Calendar.DAY_OF_MONTH));
      System.out.println("本周几:" + cal.get(Calendar.DAY_OF_WEEK));
      System.out.println("今年的第 N天 :" + cal.get(Calendar.DAY_OF_YEAR));
      System.out.println("DAY_OF_WEEK_IN_MONTH:"
            + cal.get(Calendar.DAY_OF_WEEK_IN_MONTH));
      System.out.println("----Hour-----");
      System.out.println("Hour:" + cal.get(Calendar.HOUR));
      System.out.println("HOUR_OF_DAY:" + cal.get(Calendar.HOUR_OF_DAY));
      System.out.println("----MINUTE-----");
      System.out.println("MINUTE:" + cal.get(Calendar.MINUTE));

      System.out.println();
      cal.set(Calendar.MONTH,cal.get(Calendar.MONTH)+1);
      System.out.println("向后推迟一个月(方式1)：" + sdf.format(cal.getTime()));
      cal.add(Calendar.MONDAY, 1);
      System.out.println("向后推迟一个月(方式2)：" + sdf.format(cal.getTime()));
      
      cal.set(Calendar.HOUR,cal.get(Calendar.HOUR)+1);
      System.out.println("向后推迟一小时(方式1)：" + sdf.format(cal.getTime()));
      cal.add(Calendar.HOUR, -1);
      System.out.println("向前推迟一小时(方式2)：" + sdf.format(cal.getTime()));
      
      cal.set(Calendar.MINUTE,30);
      cal.set(Calendar.SECOND,00);
      System.out.println("设置为30分钟：" + sdf.format(cal.getTime()));
      cal.getTimeInMillis();
      
      System.out.println();
      Calendar calStart = Calendar.getInstance();
      calStart.set(2014, Calendar.DECEMBER, 15);
      System.out.println("开始时间：" + sdf.format(calStart.getTimeInMillis())
            + ",毫秒数：" + calStart.getTimeInMillis());
      Calendar calEnd = Calendar.getInstance();
      calEnd.set(2016, Calendar.DECEMBER, 5, 12, 15, 35);
      System.out.println("结束时间：" + sdf.format(calEnd.getTimeInMillis())
            + ",毫秒数：" + calEnd.getTimeInMillis());
      int day =getDaysBetween(calEnd,calStart);
      System.out.println("相差天数：" + day);
      
      //计算某一月份的最大天数    
      System.out.println();
      Calendar time=Calendar.getInstance();     
      time.clear(); // 在使用set方法之前，必须先clear一下，否则很多信息会继承自系统当前时间
      time.set(Calendar.YEAR, 2016);
      int dayCount = time.getActualMaximum(Calendar.DAY_OF_MONTH);// 本月份的天数
      System.out.println("本月最大天数：" + dayCount);
      
   }

   /**
    * 计算两个时间之间相隔天数（不够精确）
    * 
    * @param startday
    *            开始时间
    * @param endday
    *            结束时间
    * @return
    */
   public static int getIntervalDays(Calendar startday, Calendar endday) {
      // 确保startday在endday之前
      if (startday.after(endday)) {
         Calendar cal = startday;
         startday = endday;
         endday = cal;
      }
      // 分别得到两个时间的毫秒数
      long sl = startday.getTimeInMillis();
      long el = endday.getTimeInMillis();

      long ei = el - sl;
      // 根据毫秒数计算间隔天数
      return (int) (ei / (1000 * 60 * 60 * 24));
   }
   
   /**
    * 计算两个时间之间相隔天数（不够精确）
    * 
    * @param startday
    *            开始时间
    * @param endday
    *            结束时间
    * @return
    */
   public int getIntervalDays(Date startday, Date endday) {
      // 确保startday在endday之前
      if (startday.after(endday)) {
         Date cal = startday;
         startday = endday;
         endday = cal;
      }
      // 分别得到两个时间的毫秒数
      long sl = startday.getTime();
      long el = endday.getTime();

      long ei = el - sl;
      // 根据毫秒数计算间隔天数
      return (int) (ei / (1000 * 60 * 60 * 24));
   } 
       
   /**
    * 精确计算两个日期之间的天数
    * 
    * @param d1
    * @param d2
    * @return
    */
   public static int getDaysBetween(Calendar d1, Calendar d2) {
      if (d1.after(d2)) { // swap dates so that d1 is start and d2 is end
         java.util.Calendar swap = d1;
         d1 = d2;
         d2 = swap;
      }

      int days = d2.get(Calendar.DAY_OF_YEAR) - d1.get(Calendar.DAY_OF_YEAR);
      int y2 = d2.get(Calendar.YEAR);
      if (d1.get(Calendar.YEAR) != y2) {
         d1 = (Calendar) d1.clone();
         do {
            days += d1.getActualMaximum(Calendar.DAY_OF_YEAR);// 得到当年的实际天数
            d1.add(Calendar.YEAR, 1);
         } while (d1.get(Calendar.YEAR) != y2);
      }
      return days;
   } 
}

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来自为知笔记(Wiz)