java处理日期时间-白红宇

java.util.Calendar

Calendar 类是一个抽象类，它为特定瞬间与一组诸如 YEAR、MONTH、DAY_OF_MONTH、HOUR 等日历字段之间的转换提供了一些方法，并为操作日历字段（例如获得下星期的日期）提供了一些方法。瞬间可用毫秒值来表示，它是距历元（即格林威治标准时间 1970 年 1 月 1 日的 00:00:00.000，格里高利历）的偏移量。

简单示例

// 通过格式化输出日期java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-dd");Calendar cal = Calendar.getInstance();// 取当前日期。System.out.println("Today is:" + format.format(cal.getTime()));cal = Calendar.getInstance();cal.add(Calendar.DAY_OF_MONTH, -1);// 取当前日期的前一天.System.out.println("yesterday is:" + format.format(cal.getTime()));cal = Calendar.getInstance();cal.add(Calendar.DAY_OF_MONTH, +1);// 取当前日期的后一天.System.out.println("nextday is:" + format.format(cal.getTime()));

或者

java.util.Date today=new java.util.Date();   java.text.SimpleDateFormat dateFormat = new java.text.SimpleDateFormat("yyyy-MM-dd");java.text.SimpleDateFormat dateTimeFormat = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println("Today is "+dateFormat.format(today));System.out.println("Now is "+dateTimeFormat.format(today));

构造特定时间

java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-dd");   Calendar calendar = new GregorianCalendar(2007, 11, 25,0,0,0);   Date date = calendar.getTime();   System.out.println("2007 Christmas is:"+format.format(date));

GregorianCalendar构造方法参数依次为：年，月-1，日，时，分，秒.

或者

java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-dd");   java.util.Date date= format.parse("2007-12-25"); System.out.println("2007 Christmas is:"+format.format(date));

取日期的每部分

int year =calendar.get(Calendar.YEAR);   int month=calendar.get(Calendar.MONTH)+1;   int day =calendar.get(Calendar.DAY_OF_MONTH);   int hour =calendar.get(Calendar.HOUR_OF_DAY);   int minute =calendar.get(Calendar.MINUTE);   int second =calendar.get(Calendar.SECOND);

取月份要加1

获取当前月份的最大天数

Calendar cal = Calendar.getInstance();   int day=cal.getActualMaximum(Calendar.DAY_OF_MONTH);   System.out.println(day);

取当月的最后一天

Calendar cal = Calendar.getInstance();   int maxDay=cals.getActualMaximum(Calendar.DAY_OF_MONTH);   java.text.Format formatter3=new java.text.SimpleDateFormat("yyyy-MM-"+maxDay);   System.out.println(formatter3.format(cal.getTime()));

取当月的第一天

java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-01");   java.util.Date firstDay=new java.util.Date();   System.out.println("the month first day is "+formats.format(firstDay));

求两个日期之间相隔的天数

java.text.SimpleDateFormat format = new java.text.SimpleDateFormat("yyyy-MM-dd");   java.util.Date beginDate= format.parse("2007-12-24");   java.util.Date endDate= format.parse("2007-12-25");   long day=(date.getTime()-mydate.getTime())/(24*60*60*1000);   System.out.println("相隔的天数="+day);

一年前的日期

java.text.Format formatter=new java.text.SimpleDateFormat("yyyy-MM-dd");   java.util.Date todayDate=new java.util.Date();   long beforeTime=(todayDate.getTime()/1000)-60*60*24*365;   todayDate.setTime(beforeTime*1000);   String beforeDate=formatter.format(todayDate);   System.out.println(beforeDate);

一年后的日期

java.text.Format formatter=new java.text.SimpleDateFormat("yyyy-MM-dd");   java.util.Date todayDate=new java.util.Date();   long afterTime=(todayDate.getTime()/1000)+60*60*24*365;   todayDate.setTime(afterTime*1000);   String afterDate=formatter.format(todayDate);   System.out.println(afterDate);

10小时后的时间

java.util.Calendar Cal=java.util.Calendar.getInstance();   Cal.setTime(dateOper);   Cal.add(java.util.Calendar.HOUR_OF_DAY,10);   System.out.println("date:"+forma.format(Cal.getTime()));

10小时前的时间

java.util.Calendar Cal=java.util.Calendar.getInstance();   Cal.setTime(dateOper);   Cal.add(java.util.Calendar.HOUR_OF_DAY,-10);   System.out.println("date:"+forma.format(Cal.getTime()));

当前日期的星期一和星期天

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd");GregorianCalendar cal = new GregorianCalendar();int dayInWeek = cal.get(Calendar.DAY_OF_WEEK);int offset = 0;if (dayInWeek == 1) {    // 星期天    offset = 6;} else {    // 星期一至星期六    offset = dayInWeek - 2;}cal.add(GregorianCalendar.DAY_OF_MONTH, -offset);String sday = dateFormat.format(cal.getTime());cal.add(GregorianCalendar.DAY_OF_MONTH, 6);String eday = dateFormat.format(cal.getTime());System.out.println("这个星期的星期一:" + sday);System.out.println("这个星期的星期天:" + eday);

获取当前日期所在的星期属于今年的第几周

GregorianCalendar cal = new GregorianCalendar();int weekOfYear = cal.get(Calendar.WEEK_OF_YEAR);System.out.println("这个星期属于第几周:" + weekOfYear);