Java中日期时间的处理

1. 获取系统时间可以通过Calendar或者Date默认构造函数或者实例得到，不过现在日期主要还是借助于Calendar来处理。另外还可以得到当前日期是一周的第几天（从星期天开始），一月以及一年的第几天

[java]

public static String getCurrentTime(){

Calendar c = Calendar.getInstance();

//HH 24 hour & hh 12 hour, E - week

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy E HH:mm:ss");

return sdf.format(c.getTime());

}

public static void printTodayInfo(){

Date date = new Date();

Calendar c = Calendar.getInstance();

c.setTime(date);

System.out.println("Time for today:"+date.toString());

System.out.println("Day for today :"+c.get(Calendar.DAY_OF_WEEK));

System.out.println("Time for today:"+c.get(Calendar.DAY_OF_MONTH));

System.out.println("Time for today:"+c.get(Calendar.DAY_OF_YEAR));

}

2. 获取相较于当前时间的历史时间，如昨天、上周、上月、去年等

[java]

public static String getYesterday(){

Calendar c = Calendar.getInstance();

c.add(Calendar.DATE, -1);

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");

return sdf.format(c.getTime());

}

public static String getLastMonth(){

Calendar c = Calendar.getInstance();

c.add(Calendar.MONTH, -1);

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");

return sdf.format(c.getTime());

}

public static String getLastYear(){

Calendar c = Calendar.getInstance();

c.add(Calendar.YEAR, -1);

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy");

return sdf.format(c.getTime());

}

3. 设置一个历史时间

[java]

public static void setDate(){

Calendar c = Calendar.getInstance();

//note that the month start from 0

c.set(2013, 0, 25, 14, 48, 20);

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

System.out.println(sdf.format(c.getTime()));

String birthdate = "01/25/2012 13:11:12";

Date date = new Date();

try {

date = sdf.parse(birthdate);

} catch (ParseException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

c.setTime(date);

System.out.println(sdf.format(c.getTime()));

}