java8 对date的支持更加好，更加清晰，不用再在calendar和date之间纠结了。

LocalDateTime datetime = LocalDateTime.now(); // datetime
LocalDate date = LocalDate.now(); // date
LocalTime time = LocalTime.now(); // time
System.out.println("datetime: "+datetime);
System.out.println("date: "+date);
System.out.println("time: "+time);

//不用calendar来会转换了，月分为枚举值，有value，有string，更清晰
Month month = datetime.getMonth(); // 月  JANUARY
int monthValue = datetime.getMonthValue();// 月value 1，
System.out.println(month);
System.out.println(monthValue);

DayOfWeek dayOfWeek = datetime.getDayOfWeek(); //week 如： SUNDAY
System.out.println(dayOfWeek);


LocalDateTime localDateTime = LocalDateTime.of(2020, 1, 0b1100, 10, 43, 20);// 新建datetime
LocalDate localDate = LocalDate.of(2020, 1, 12); // 根据年月日新建date
LocalTime localTime = LocalTime.of(10, 43, 20);  // 根据时分秒新建time
System.out.println(localDateTime);
System.out.println(localDate);
System.out.println(localTime);

Instant now = Instant.now();
long epochSecond = now.getEpochSecond(); // 秒long
long EpochMilli = now.toEpochMilli(); // 毫秒long
System.out.println(epochSecond);
System.out.println(EpochMilli);