java中日期处理方法



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()));  

}  

 

4. 时间与long型的对照关系，可以发现0对应的时间是 01/01/1970 08:00:00，以后每增加1s就要加上1000。这样借助于它我们也可以得到不同时间。

[java] 

public static void checkLongAndDate(){  

    Calendar c = Calendar.getInstance();  

    c.setTimeInMillis(0);  

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

    //output is 01/01/1970 08:00:00  

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

    c.setTimeInMillis(c.getTimeInMillis()+1000*60*60*24);  

    System.out.println(sd