Java Calendar 类的时间操作

原文地址：blog.csdn.NET/joyous/article/details/9630893

Calendar 的 month 从 0 开始，也就是全年 12 个月由 0 ~ 11 进行表示。

Calendar.SUNDAY = 1
Calendar.MONDAY = 2
Calendar.TUESDAY = 3
Calendar.WEDNESDAY = 4
Calendar.THURSDAY = 5
Calendar.FRIDAY = 6
Calendar.SATURDAY = 7

SimpleDateFormat 的格式定义

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
Y	Week year	Year	2009; 09
M	Month in year (context sensitive)	Month	July; Jul; 07
L	Month in year (standalone form)	Month	July; Jul; 07
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day name in week	Text	Tuesday; Tue
u	Day number of week (1 = Monday, ..., 7 = Sunday)	Number	1
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978
z	Time zone	General time zone	Pacific Standard Time; PST; GMT-08:00
Z	Time zone	RFC 822 time zone	-0800
X	Time zone	ISO 8601 time zone	-08; -0800; -08:00

Java Calendar 演示代码如下：

 

package demo;

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

public class Test
{
  public Test()
  {
  }

  public static void main(String[] args)
  {
    // 字符串转换日期格式
    // DateFormat fmtDateTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    // 接收传入参数
    // String strDate = args[1];
    // 得到日期格式对象
    // Date date = fmtDateTime.parse(strDate);

    // 完整显示今天日期时间
    String str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS")).format(new Date());
    System.out.println(str);

    // 创建 Calendar 对象
    Calendar calendar = Calendar.getInstance();

    try
    {
      // 对 calendar 设置时间的方法
      // 设置传入的时间格式
      SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-M-d H:m:s");
      // 指定一个日期
      Date date = dateFormat.parse("2013-6-1 13:24:16");
      // 对 calendar 设置为 date 所定的日期
      calendar.setTime(date);

      // 按特定格式显示刚设置的时间
      str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS")).format(calendar.getTime());
      System.out.println(str);
    }
    catch (ParseException e)
    {
      e.printStackTrace();
    }

    // 或者另一種設置 calendar 方式
    // 分別爲 year, month, date, hourOfDay, minute, second
    calendar = Calendar.getInstance();
    calendar.set(2013, 1, 2, 17, 35, 44);
    str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS")).format(calendar.getTime());
    System.out.println(str);

    // Calendar 取得当前时间的方法
    // 初始化 (重置) Calendar 对象
    calendar = Calendar.getInstance();
    // 或者用 Date 来初始化 Calendar 对象
    calendar.setTime(new Date());

    // setTime 类似上面一行
    // Date date = new Date();
    // calendar.setTime(date);

    str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS")).format(calendar.getTime());
    System.out.println(str);

    // 显示年份
    int year = calendar.get(Calendar.YEAR);
    System.out.println("year is = " + String.valueOf(year));

    // 显示月份 (从0开始, 实际显示要加一)
    int month = calendar.get(Calendar.MONTH);
    System.out.println("nth is = " + (month + 1));

    // 本周几
    int week = calendar.get(Calendar.DAY_OF_WEEK);
    System.out.println("week is = " + week);

    // 今年的第 N 天
    int DAY_OF_YEAR = calendar.get(Calendar.DAY_OF_YEAR);
    System.out.println("DAY_OF_YEAR is = " + DAY_OF_YEAR);

    // 本月第 N 天
    int DAY_OF_MONTH = calendar.get(Calendar.DAY_OF_MONTH);
    System.out.println("DAY_OF_MONTH = " + String.valueOf(DAY_OF_MONTH));

    // 3小时以后
    calendar.add(Calendar.HOUR_OF_DAY, 3);
    int HOUR_OF_DAY = calendar.get(Calendar.HOUR_OF_DAY);
    System.out.println("HOUR_OF_DAY + 3 = " + HOUR_OF_DAY);

    // 当前分钟数
    int MINUTE = calendar.get(Calendar.MINUTE);
    System.out.println("MINUTE = " + MINUTE);

    // 15 分钟以后
    calendar.add(Calendar.MINUTE, 15);
    MINUTE = calendar.get(Calendar.MINUTE);
    System.out.println("MINUTE + 15 = " + MINUTE);

    // 30分钟前
    calendar.add(Calendar.MINUTE, -30);
    MINUTE = calendar.get(Calendar.MINUTE);
    System.out.println("MINUTE - 30 = " + MINUTE);

    // 格式化显示
    str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SS")).format(calendar.getTime());
    System.out.println(str);

    // 重置 Calendar 显示当前时间
    calendar.setTime(new Date());
    str = (new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SS")).format(calendar.getTime());
    System.out.println(str);

    // 创建一个 Calendar 用于比较时间
    Calendar calendarNew = Calendar.getInstance();

    // 设定为 5 小时以前，后者大，显示 -1
    calendarNew.add(Calendar.HOUR, -5);
    System.out.println("时间比较：" + calendarNew.compareTo(calendar));

    // 设定7小时以后，前者大，显示 1
    calendarNew.add(Calendar.HOUR, +7);
    System.out.println("时间比较：" + calendarNew.compareTo(calendar));

    // 退回 2 小时，时间相同，显示 0
    calendarNew.add(Calendar.HOUR, -2);
    System.out.println("时间比较：" + calendarNew.compareTo(calendar));
  }
}

要计算时间差，可用 Calendar.getTimeInMillis() 取得两个时间的微秒级的时间差，再加以换算即可，比如获得相差天数，代码如下：

[java] view plain copy