//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);