Java SE 8 Date/Time API

Question 1

What does java.time.LocalDate represents?

Answer 1

represents a date without time or time zone. (YYYY-MM-DD)

Question 2

What does java.time.LocalTime represents?

Answer 2

time without dates or time zones (HH:MM:SS.nanosecond)

Question 3

What does java.time.LocalDateTime represents?

Answer 3

represents both date and time without time zones (YYYY-MM-DD HH:MM:SS.nanosecond)

Question 4

What is the difference between LocalDateTime and Instant?

Answer 4

LocalDateTime uses the default time zone, but Instant doesn’t.(Use UTC as timezone)

Question 5

What is the java.time.Period used for?

Answer 5

Used to measure an amount of time in terms of year, months and days

ex:

LocalDate manufacturingDate = LocalDate.of(2016, Month.JANUARY, 1);
LocalDate expiryDate = LocalDate.of(2018, Month.JULY, 18);
Period expiry = Period.between(manufacturingDate, expiryDate);

Question 6

What is the Duration class used fr?

Answer 6

Represents time in terms of hour, minutes, seconds and so on ex:

LocalDateTime comingMidnight =
LocalDateTime.of(LocalDate.now().plusDays(1), LocalTime.MIDNIGHT);
LocalDateTime now = LocalDateTime.now();

Duration between = Duration.between(now, comingMidnight);

Question 7

What is TemporalUnit interface used for?

Answer 7

It represents date or time units such as seconds, hours, days, months, years and son on. The ChronoUnit implements this interface

Question 8

What are the three import classed related to time zones?

Answer 8

ZoneId, ZoneOffSet, ZonedDateTime

Question 9

What does ZoneId class represents?

Answer 9

represent time zones. Time zones are typically idfentified as using offset from Greenwich Mean Time (GTM, UTC/Greenwhich)

ZoneId AsiaKolkataZoneId = ZoneId.of(“Asia/Kolkata”);

Question 10

What does ZoneOffset class represents?

Answer 10

represents the time-zone offset from UTC/Greenwich.

Question 11

What does ZonedDateTime represents?

Answer 11

date, time and timezone

Question 12

What class do you use to format date and time?

Answer 12

DateTimeFormatter

ex.

LocalTime wakeupTime = LocalTime.of(6, 0, 0);
System.out.println(“Wake up time: “ + DateTimeFormatter.ISO_TIME.format(wakeupTime));

Question 13

What are the pre-defined constant for formatting date and time values?

Answer 13

• ISO_DATE (2015-11-05)
• ISO_TIME (11:25:47.624)
• RFC_1123_DATE_TIME (Thu, 5 Nov 2015 11:27:22 +0530)
• ISO_ZONED_DATE_TIME (2015-11-05T11:30:33.49+05:30[Asia/Kolkata])

Question 14

What to do if you want a custom format of DateTimeFormatter?

Answer 14

you may use the ofPattern() method

DateTimeFormatter customFormat = DateTimeFormatter.ofPattern(“dd MMM yyyy”);
System.out.println(customFormat.format(LocalDate.of(2016, Month.JANUARY, 01)));

Question 15

What is the representation of these Periods toString()?

a) Period.ofMonths(3)
b) Period.of(0, 20, 47)
c) Period.ofWeeks(3)

Answer 15

a) P3M
b) P20M47D
c) P21D

Question 16

What is the representation of these Duration(time) to string?

a) Duration.ofDays(1)
b) Duration.ofHours(1)
c) Duration.ofMinutes(1)
d) Duration.ofSeconds(10)
e) Duration.ofMillis(1)
f) Duration.ofNanos(1)

Answer 16

a) PT24H
b) PT1H
c) PT1M
d) PT10S
e) PT0.001S
f) PT0.000000001S

Question 17

Fill in the blank:

Once you hate the NumberFormatInstance you can call ____ to turn a number into a String and ____ to return a string into a number

Answer 17

• format()

- parse()

Question 18

How are Period and Duration different when considering daylight savings when added to ZonedDateTime

Answer 18

• A Duration will add an exact number of seconds, thus a duration of one day is always exactly 24 hours. By contrast, a Period will add a conceptual day, trying to maintain the local time.
• For example, consider adding a period of one day and a duration of one day to 18:00 on the evening before a daylight savings gap. The Period will add the conceptual day and result in a ZonedDateTime at 18:00 the following day. By contrast, the Duration will add exactly 24 hours, resulting in a ZonedDateTime at 19:00 the following day (assuming a one hour DST gap).