Java 8 Date-Time API

Date-Time
(JSR-310)
By – Anindya Bandopadhyay
Java SE 8 isn't the same Java we know.

Date Time (JSR-310)

Why another set of Date Time ?
• Date and Calendar class didn’t have adequate
support.
• Date and Calendar objects are not thread safe.
• Date and Calendar didn’t allow different
calendar system like Japanese, Thai Buddhist
and other calendars.

What is Java 8 Date-Time offering ?
(JSR-310)

Object are immutable as a result they
are thread safe.

API’s are more organize and error free.

It allow different calendar system like
Japanese, Thai Buddhist and other
calendars.

Possible to write custom query against
new Date-Time

It provide accuracy at the range of
nano second.

Basic understanding of Date-Time
• In Java 8 Date-Time have representation of
two type.
• One way of represents Date-Time is in human
terms such as year, month, day, hour, minute
and second.
• Other way is in machine terms, measures time
continuously along a timeline from an origin,
called the epoch, in nanosecond resolution.

What is epoch ?
• In the fields of chronology and periodization,
an epoch is an instant in time chosen as the
origin of a particular era. The "epoch" then
serves as a reference point from which time is
measured.
• For us it is Unix Time [Epoch Time].

What is Unix time ?
• Unix time (also known as POSIX time or Epoch
time) is a system for describing instants in
time, defined as the number of seconds that
have elapsed since 00:00:00 Coordinated
Universal Time (UTC), Thursday, 1 January
1970,[1][note 1] not counting leap seconds.
1st Jan 1970 Midnight Current UTC time

Problem because of epoch time

Something interesting
Source of information is Independent.
http://www.independent.co.uk/life-
style/gadgets-and-tech/news/facebook-46-
years-notifications-why-social-network-told-
users-they-had-been-friends-for-decades-and-
a6792661.html

Overview of java.time package
• java.time - the base package containing the value
objects
• java.time.chrono -provides access to different calendar
systems [like Thai Buddhist ]
• java.time.format - allows date and time to be
formatted and parsed
• java.time.temporal - the low level framework and
extended features
• java.time.zone - support classes for time-zones

LocalDate
This object only contain date
component.

It is consist of Day, Month, Year.

What is today date ?
• LocalDate today = LocalDate.now();
• System.out.println("Today's Date : "+ today);
• Output :- “Today's Date : 2016-01-12”

What is previous date ?
• System.out.println("Previous Date : "+
today.minusDays(1));
• Output :- “Previous Date : 2016-01-11”

What is next date ?
• System.out.println("Next Date : "+
today.plusDays(1));
• Output :- “Next Date : 2016-01-13”

What is the length of year ?
• System.out.printf("%s days in %s
n",today.lengthOfYear(),today.getYear());
• Output :- “366 days in 2016”

Is leap year ?
• System.out.printf("%s is leap year ? %s
n",today.get(ChronoField.YEAR),
today.isLeapYear());
• Output :- “2016 is leap year ? true”

LocalTime
• This object only contain time component.
• It is consist of hour, minute and second.
• E.g. What is the time now ? “05:40 AM”

What is the time ‘now’ ?
• LocalTime timeNow = LocalTime.now();
• System.out.println("Time now : "+ timeNow);

Simply add an hour to current time
• System.out.println("Meeting in next hour : "+
timeNow.plus(1, ChronoUnit.HOURS));

Only take out minutes
• System.out.println("Only upto minutes : "+
timeNow.truncatedTo(ChronoUnit.MINUTES));

LocalDateTime
• This object contain date and time
components.
• It is consist of year,month,day,hour, minute
and second.

LocalDate, LocalTime and
LocalDateTime objects doesn’t contain
information regarding time-zone. As it
is ‘Local’.

Time Zone
• Numerous of Time-Zones are covered.
• These Time-Zones are govern by political
rules.
• These rules are complex and might frequently
change.
• E.g. In Brazil before 2008, there were no fixed
start and end dates for DST.

Multiple group provide rules
• Time Zone DB
• Windows
• International Air Transport Association (IATA)
Note :- With JDK update time-zone database get
updated locally.

Zone Id
• A ZoneId is used to identify the rules used to
convert between an Instant and a
LocalDateTime.
• It is replacement for TimeZone class.
• Eg. “Asia/Calcutta” , “Etc/GMT-1”

ZoneOffset
• This object represent the time zone difference
from Greenwich/UTC.
• This is usually a fixed number of hours and
minutes.

ZoneDateTime
• It contain date and time along with time zone
details.

Year
• This object contain only Year information.
Which year is this ?
2016

YearMonth
• This object contains year and month
component only.

Credit Card expire date : 2019-11

MonthDay
• This object represent month and day
component only.

AMEX Card billing cycle : --02-22

OffsetTime
• This object represents time and offset from
UTC/GMT.
22:52:58.868+05:30

OffsetDateTime
• This object represents date , time and offset
from UTC/GMT.
2016-01-17T22:42:50.541+05:30

Instance
• This object represent timestamp and it is used
where we need to record any event
timestamp in the application.

Get the time in Epoch seconds : 1453812691

Clock
• This object return current system timestamp.
• This object allows to inject a real or fake clock
into other java.time objects.
• This class can be used for unit testing.

Output is in next slide

• Get an Instant from clock object =>2016-01-26T13:06:35.776Z
• Create an Instant from the reference of clock object =>2016-
01-26T13:06:35.792Z
• Create an LocalDateTime from the reference of clock object
=>2016-01-26T18:36:35.792
• Create an ZonedDateTime from the reference of clock object
=>2016-01-26T18:36:35.792+05:30[Asia/Calcutta]
• Create an OffsetDateTime from the reference of clock object
=>2016-01-26T18:36:35.792+05:30

toString() method return string in ISO
8601 format

Commonly Used Methods
Prefix Method Type Use
of
static
factory
Creates an instance where the factory is primarily validating the input parameters,
not converting them.
from
static
factory
Converts the input parameters to an instance of the target class, which may involve
losing information from the input.
parse
static
factory Parses the input string to produce an instance of the target class.
format instance
Uses the specified formatter to format the values in the temporal object to produce a
string.
get instance Returns a part of the state of the target object.
is instance Queries the state of the target object.
with instance
Returns a copy of the target object with one element changed; this is the immutable
equivalent to a set method on a JavaBean.
plus instance Returns a copy of the target object with an amount of time added.
minus instance Returns a copy of the target object with an amount of time subtracted.
to instance Converts this object to another type.
at instance Combines this object with another.

Formatting and Parsing
• format method coverts a temporal based
object to a string representation using the
specified format.
• parse method covert a string date/time to
temporal based object.

DateTimeFormatter
• This class is primarily responsible for
formatting.
• DateTimeFormatterBuilder class allow a
DateTimeFormatter to be created.
• Formatter can be created with desired Locale,
Chronology, ZoneId and DecimalStyle.

Output:-
Date formatting -> Dec 20 2001 4 AD
Time formatting -> 11:23 PM
Date-Time Formatting

Date-Time Parsing
Output :-
Date parsing -> 2001-12-20
Time parsing -> 23:23

Temporal
• java.time.temporal package support date,
time code and in particular date time
calculations.

Temporal Type
• Application code should NOT declare variable
type as temporal interface. Unless application
code doing something as very basic level. (E.g.
Doing calculation)

TemporalAdjuster
• This interface provide method to take a
temporal value and return an adjuster.
• To create custom adjuster need to implement
TemporalAdjuster interface.
• Temporal adjustInto(Temporal temporal)

TemporalAdjusters (Plural)
• This class provide predefine adjusters.
• Eg.  first day of month/year, last day of
month/year, next Sunday

Custom Adjuster
Output :- 2016-02-28

TemporalQuery<R>
• This interface can be used to retrieve
information from a temporal based object.
• R queryFrom(TemporalAccessor temporal)

Output :- Is holiday ? -> true
Custom Query

TemporalQueries (Plural)
• This class provide predefine queries.
• E.g.  offset , precision query

Output

Period
• Period represent amount of time in terms of
years, months and days.

How many days passed after taken 2016 new year resolution ?
P16D

Duration
• Duration represent amount of time in terms of
seconds and nano-seconds.

Duration between two time : PT0.1S

Converting to a Non-ISO-Based Date
Output :-

Interoperability with Legacy Code
• Calendar.toInstant() converts the Calendar object to an Instant.
• GregorianCalendar.toZonedDateTime() converts a GregorianCalendar
instance to a ZonedDateTime.
• GregorianCalendar.from(ZonedDateTime) creates a GregorianCalendar
object using the default locale from a ZonedDateTime instance.
• Date.from(Instant) creates a Date object from an Instant.
• Date.toInstant() converts a Date object to an Instant.
• TimeZone.toZoneId() converts a TimeZone object to a ZoneId.

Look time piece makers .. How much you can make

Java 8 Date-Time API

More Related Content

What's hot

Viewers also liked

Similar to Java 8 Date-Time API

Recently uploaded

In this document

Java 8 Date-Time API