Java中Calendar/SimpleDateFormat/Date常用方法总结

 //获取当前时刻yyyy-MM-dd HH:mm:ss
 Calendar calendar = Calendar.getInstance();
 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");// 设置日期格式
 String now = sdf.format(calendar.getTime());
 System.out.println(now);

 //获取当前时刻yyyy-MM-dd
 Calendar calendar = Calendar.getInstance();
 SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd");// 设置日期格式
 String now1 = sdf1.format(calendar.getTime());
 System.out.println(now1);

 //获取当前时刻yyyy-MM
 Calendar calendar = Calendar.getInstance();
 SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM");// 设置日期格式
 String now2 = sdf2.format(calendar.getTime());
 System.out.println(now2);

 //获取当前时刻,年月日
 Calendar calendar = Calendar.getInstance();
 int year = calendar.get(Calendar.YEAR);
 int month = calendar.get(Calendar.MONTH) + 1;
 int day = calendar.get(Calendar.DAY_OF_MONTH);
 System.out.println(year + "-" + month + "-" + day);

 //获取当前时刻时间戳
 Calendar calendar = Calendar.getInstance();
 long ts = calendar.getTimeInMillis();
 System.out.println(ts);

 //获取上个月yyyy-MM
 Calendar calendar = Calendar.getInstance();
 calendar.add(Calendar.MONTH, -1);
 String lastMonth = new SimpleDateFormat("yyyy-MM").format(calendar.getTime());
 System.out.println(lastMonth);

 //获取昨天yyyy-MM-dd
 Calendar calendar = Calendar.getInstance();
 calendar.add(Calendar.DATE, -1);
 String yesterday = new SimpleDateFormat("yyyy-MM-dd").format(calendar.getTime());
 System.out.println(yesterday);

 //将指定年月日时分秒转换成时间戳
 SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 Date date = simpleDateFormat.parse("2015-05-01 00:00:00");
 long ts1 = date.getTime();
 System.out.println(ts1);
 //或者
 Calendar calendar = Calendar.getInstance();
 calendar.set(2015, 4, 1, 0, 0, 0);     //此处4即代表5月
 long ts2 = calendar.getTimeInMillis();
 System.out.println(ts2);

 //将指定时间戳转化为年月日时分秒
 SimpleDateFormat format = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" );
 long ts = 1234567899L;
 String date = format.format(ts);
 Date date1 = format.parse(date);
 System.out.println("Format To String(Date):" + date);
 System.out.println("Format To Date:" + date1);