4. Dates, Times, Locales and Resource bundles

Question 1

How are the classes in java.time organised?

Answer 1

• Local dates and times: these dates are local to your time zone, the classes: LocalDate, LocalTime, LocalDateTime
• Zoned dates and times: these dates include time-zone information, the classes:
  ZonedDateTime and OffsetDateTime
• Formatters for dates and times: you can parse dates with patterns and in a variety of styles,
  the classes: format.DateTimeFormatter
• Adjustments to dates and times: you can adjust and manipulate dates and times by handy
  increments, the classes: temporal.TemporalAdjusters and temporal.ChronoUnit
• Periods, Durations: represent an amount of time, periods for days or longer and durations
  for shorter periods (minutes seconds), classes: Periods and Durations
• Instants: represent a specific instant in time, so you can compute the number of minutes
  between two instants, the class: Instants

Question 2

What does the LocalDate.parse(String string) do?

Answer 2

to parse a string that matches the date (so string need to be in the order of ISO-
8601)

Question 3

What does the LocalDate.of(YYYY-MM-DD) do?

Answer 3

to parse a string that matches the date (so string need to be in the order of ISO-
8601)

Question 4

What are ZoneRules for?

Answer 4

With ZoneRules the class captures the current rules about daylight savings in various parts of the
world. It gives answer on the question is the current ZoneId in daylight savings time?

Question 5

What are ZoneRules for?

Answer 5

With ZoneRules the class captures the current rules about daylight savings in various parts of the
world. It gives answer on the question is the current ZoneId in daylight savings time?

Question 6

Which Adjustments are there?

Answer 6

You can add days and hours with handy methods of LocalDate and ZonedDateTime classes, suchs as
plusMinutes(). plusYears(), minusWeeks(), minusSeconds().

Question 7

What are temporalAdjusters?

Answer 7

The class temporalAdjusters has a whole slew of handy methods to make a TemporalAdjuster for a
variety of scenarios, such as firstDayOfNextYear(), lastDayOfMonth()

Question 8

What is a Period?

Answer 8

The Period Class in Java class obtains a quantity or amount of time in terms of years, months and days.

Question 9

What is the output of Period?

Answer 9

Output of Periods is P for instance P1D, P1Y

Question 10

What will the minus() method do?

Answer 10

You can call the minus() method on ZonedDateTime and DateTime classes with an argument of a
Period to minus that period on the current DateTime.

Question 11

What is a Duration?

Answer 11

A Duration object ( java. time. Duration ) represents a period of time between two Instant objects.

Question 12

What is the output of a Duration?

Answer 12

If you print out the Duration object you will get something like this: PT1H18M. PT means period of
time, 1H18M, means 1 hour 18 minutes.

Question 13

What is an Instance?

Answer 13

An instant represent an instant in time. (seconds and nano seconds)

Question 14

How to create a LocalDate?

Answer 14

LocalDate.now();
LocalDate.of(2017, 8, 21);
LocalDate.parse(“2017-08-21”);

Question 15

How to create a LocalTime?

Answer 15

LocalTime.now();
LocalTime.of(10, 19, 36);
LocalTime.parse(“10:19:36”);

Question 16

How to create a LocalDateTime?

Answer 16

LocalDateTime.now();
LocalDateTime.of(aDate, aTime);
LocalDateTime.parse(“2017-04-08T10:19:36);
LocalDateTime.parse(aDateTime, a Formatter);

Question 17

How to create a ZonedDateTime?

Answer 17

ZonedDateTime.now();

ZonedDateTime.of(aDateTime, ZoneId.of(aZoneString);

Question 18

How to create a DateTimeFormatter?

Answer 18

DateTimeFormatter.ofPattern(“yyyy-MM-dd HH:mm”;

DateTimeFormatter.ofLocalizedDateTime(FormatStyle.SHORT).withLocale(aLocale);

Question 19

How to create an Instant?

Answer 19

Instant.now();
zonedDateTime.toInstant();
aDateTime.toInstant();

Question 20

how to create a Period?

Answer 20

Period.between(aDate1, aDate2);

Period.ofDays(2);

Question 21

How to create a Duration?

Answer 21

Duration.between(aTime1, aTime2);

Duration.ofMinutes(3);

Question 22

What are the key adjustments of LocalDate?

Answer 22

aDate.minusDays(3);
aDate.plusWeeks(2);
aDate.withYear(2018);

Question 23

What are the key adjustments of LocalDate?

Answer 23

aTime.minus(3, ChronoUnit.MINUTES);
aTime.plusMinutes(3);
aTime.withHour(12);

Question 24

What are the key adjustments of LocalDateTime?

Answer 24

aDateTime.minusDays(3);
aDateTime.plusMinutes(3);
aDateTime.plus(Duration.ofMinutes(4));
aDateTime.withMonth(2);

Question 25

Which 2 Constructors does Locale have?

Answer 25

• Locale(String language)

- Locale(String language, String country)

Question 26

What does getCountry(); return?

Answer 26

getCountry(); geeft de afkorting van het land terug.

Question 27

What does getDisplayCountry() terug?

Answer 27

getDisplayCountry(); geeft de naam van het land

voluit terug. Geldt hetzelfde voor language.

Question 28

Are DateTime object mutable?

Answer 28

• Datetime objects are immutable so you can’t modify it

Question 29

When do you get ZoneRulesException?

Answer 29

• Je krijgt een ZoneRulesException bij een foute zoneId

Question 30

Which 3 property files does java know?

Answer 30

• System level properties file (not on the exam)
• Java.util.Properties: makes it easy for a programmer to create and maintain property files for
  whatever applications the programmer chooses.

- Java.util.ResourceBundle: that can use the Properties class to make it easier for a
programmer to add localization and/or internationalization features to application.

Question 31

What is the structure of a property file?

Answer 31

• Set of comments (# or !)
• Followed by a number of rows of tekst data (each row representing a key/value pair)

Key = value
Key : value
Key value

Question 32

What wil the property.list(); return?

Answer 32

propertie.list(); will produce an output of a list of key/value pairs

Question 33

What does the String getProperty(String key) method do?

Answer 33

Returns the property associated with the key

Question 34

What does the void load(InputStream is) method do?

Answer 34

reads a property list (key and element pairs) from the input byte stream

Question 35

What does the Object setProperty(String key, String value) method do?

Answer 35

This wel set the property

Question 36

What does the void store(OutputStream out, String headerComment) method do?

Answer 36

writes this property list (key and element
pairs) in this Properties table to the output stream in a format suitable for loading into a Properties table using the
load(InputStream) method

Question 37

What are 2 rules when using ResourceBundle?

Answer 37

• These files must end in “.properties”
• The end of the name before the “.properties” must be a string that start with an underscore
  and then declares the Locale the file represents (for example: MyApp_nl.properties).

Question 38

What happens when we use ResourceBundle.getBundle(); without a Locale?

Answer 38

• These files must end in “.properties”
• The end of the name before the “.properties” must be a string that start with an underscore
  and then declares the Locale the file represents (for example: MyApp_nl.properties).

Question 39

How does Java look for the bundles?

Answer 39

• Start with the full Locale requested (first .java then .properties)
• Then fallback to just Language (first .java then .properties)
• Then fallback to the default Locale (first .java then .properties)
• Then fallback to the default bundle (first .java then .properties)
• Then cry: MissingResourceException