Jdk8 brings new time utility classes, including LocalDateTime, LocalDate, and LocalTime. Here’s a look at how common usage is used on the new utility class.

1. Obtain the current time

LocalDateTime.now()
LocalDate.now()
LocalTime.now()
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Getting the current time is as simple as calling the now method, and the code runs as follows

The T16 2019-08-23: was. 439679 2019-08-23 16:17:18. 441228Copy the code

2. Obtain the time of another time zone

1 Obtain the UTC time

LocalDateTime.now(ZoneId.of("UTC"))
LocalDate.now(ZoneId.of("UTC"))
LocalTime.now(ZoneId.of("UTC"))
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The result is as follows

The 2019-08-23 T08: all the 2019-08-23 08:20:34 065057. 065973Copy the code

As you can see, it is 8 hours less than the first time. Because Beijing time is 8 east, it is 8 hours more than utc time.

2 Obtain the time of other time zones based on utc

LocalDateTime.now(ZoneId.of("+ 7"))
LocalDate.now(ZoneId.of("+ 7"))
LocalTime.now(ZoneId.of("+ 7"))
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Other time zones are easy to obtain according to the UTC standard: + for the East and – for the West;

3. Time formatting and string conversion time

1 Formatting Time

DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").format(LocalDateTime.now())
DateTimeFormatter.ofPattern("yyyy_MM_dd").format(LocalDate.now())
DateTimeFormatter.ofPattern("HHmmss").format(LocalTime.now())
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DateTimeFormatter is a utility class that defines the time format. All three classes can be used, but be careful that LocalDate does not define a time format, and LocalTime does not define a date format, otherwise an error will be reported.

2 Format the string transfer time

LocalDateTime.parse("20190801000000", DateTimeFormatter.ofPattern("yyyyMMddHHmmss"))
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4. Time required for creating a vm

LocalDateTime.of(2018, 8, 13, 23, 56, 2)
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According to the year, month, day, hour, minute, second can directly create a time, very convenient.

5. Time and timestamp conversion

1. Time to timestamp

LocalDateTime.now().toInstant(ZoneOffset.of("+ 8")).toEpochMilli()
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2. Timestamp to time

LocalDateTime.ofInstant(Instant.ofEpochMilli(1566550144837L), ZoneId.systemDefault())
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6. Time calculation

1. Get a year, month, day, hour, minute, second property of a certain time

LocalDateTime now = LocalDateTime.now();
now.getYear();
now.getMonth();
now.getDayOfMonth();
now.getDayOfYear();
now.getDayOfWeek();
now.getHour();
now.getMinute();
now.getSecond();
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2. Calculate the increase or decrease of a date

LocalDateTime now = LocalDateTime.now(); // Add a year now.plusYears(1); // Reduce a year now.minusyears (1); // Add now.plusmonths (1); // Reduce now.minusmonths (1); .Copy the code

3. Calculate the difference between two dates

LocalDateTime time1 = LocalDateTime.of(2019, 8, 31, 0, 0);
LocalDateTime time2 = LocalDateTime.of(2019, 7, 31, 0, 0);
System.out.println(time1.until(time2,ChronoUnit.DAYS));

result : -31
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It’s easy to calculate the number of days between two dates, as well as any other value you want to calculate.

4. Calculate where to leave a little Easter egg

LocalDateTime time2 = LocalDateTime.now().minusDays(1);
LocalDateTime time1 = LocalDateTime.now();
System.out.println(time2.until(time1,ChronoUnit.DAYS));

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LocalDateTime time1 = LocalDateTime.now();
LocalDateTime time2 = LocalDateTime.now().minusDays(1);
System.out.println(time2.until(time1,ChronoUnit.DAYS));
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Look at the two calculated results. They are different from what you think.

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