获得当前时间

获得当前时间戳：

1、new Date().getTime()

2、System.currentTimeMillis()

3、Calendar calendar = Calendar.getInstance();

     calendar.getTimeInMillis()

获得当前时间：

Calendar calendar = Calendar.getInstance();

calendar.get(Calendar.YEAR)//年

calendar.get(Calendar.MONTH)//月

calendar.get(Calendar.DATE)//日

calendar.get(Calendar.HOUR)//时

calendar.get(Calendar.MINUTE)//分

calendar.get(Calendar.SECOND)//秒

calendar.get(Calendar.MILLISECOND)//毫秒

获取当前时间，带格式：

    publicstaticvoid main(String[]args){

       DateFormat dateFormat1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

       System.out.println(dateFormat1.format(new Date()));

       System.out.println(dateFormat1.format(Calendar.getInstance().getTime()));

       DateFormat dateFormat2 = new SimpleDateFormat("yyyy年-MM月-dd日 HH:mm:ss");

       System.out.println(dateFormat2.format(new Date()));

       System.out.println(dateFormat2.format(Calendar.getInstance().getTime()));

    }

一段时间前或后：

       Calendar calendar = Calendar.getInstance();

       //一年前

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

       //两个月后

       calendar.add(Calendar.MONTH, 2);

通过毫秒数获取时间：

       Date date = new Date(1418870012469L);

       DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

       System.out.println(dateFormat.format(date));

或：

       Calendar calendar = Calendar.getInstance();

       calendar.setTimeInMillis(1404564546487L);

       DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

       System.out.println(dateFormat.format(calendar.getTime()));

---

字符串转Calendar：

   publicstaticvoid main(String[]args) throws ParseException{

          DateFormat dateFormat1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

          Date date1 = dateFormat1.parse("2015-04-20 00:00:01");

          Calendar calendar1 = Calendar.getInstance();

          calendar1.setTime(date1);

          DateFormat dateFormat2 = new SimpleDateFormat("yyyy-MM-dd");

          Date date2 = dateFormat2.parse("2015-04-20");

          Calendar calendar2 = Calendar.getInstance();

          calendar2.setTime(date2);

          System.out.println(calendar1.getTimeInMillis());

          System.out.println(calendar2.getTimeInMillis());

   }

输出：

1429459201000

1429459200000

从输出可看出不带时间时默认是0时0分0秒

Calendar转字符串：

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

Calendar calendar = Calendar.getInstance();

String timeStr = dateFormat.format(calendar.getTime());

---

Calendar转Date：

Calendar calendar = Calendar.getInstance();

Date date = calendar.getTime();

Date转Calendar：

Date date = new Date();

Calendar calendar = Calendar.getInstance();

calendar.setTime(date);

或：

Date date = new Date();

Calendar calendar = Calendar.getInstance();

calendar.setTimeInMillis(date.getTime());