Java 8 Date Time API Example Tutorial – LocalDate, Instant, LocalDateTime, Parse and Format
Java 8 Date and Time API is one of the most sought after change for developers. Java has been missing a consistent approach for Date and Time from start and Date Time API is a welcome addition to the core Java APIs.
Why do we need new Java Date Time API?
Before we start looking at the Java 8 Date Time API, let’s see why do we need a new API for this. There have been several problems with the existing date and time related classes in java, some of them are:
- Java Date Time classes are not defined consistently, we have Date Class in both
java.util
as well asjava.sql
packages. Again formatting and parsing classes are defined injava.text
package. java.util.Date
contains both date and time, whereasjava.sql.Date
contains only date. Having this injava.sql
package doesn’t make sense. Also both the classes have same name, that is a very bad design itself.- There are no clearly defined classes for time, timestamp, formatting and parsing. We have
java.text.DateFormat
abstract class for parsing and formatting need. UsuallySimpleDateFormat
class is used for parsing and formatting. - All the Date classes are mutable, so they are not thread safe. It’s one of the biggest problem with Java Date and Calendar classes.
- Date class doesn’t provide internationalization, there is no timezone support. So
java.util.Calendar
andjava.util.TimeZone
classes were introduced, but they also have all the problems listed above.
There are some other issues with the methods defined in Date and Calendar classes but above problems make it clear that a robust Date Time API was needed in Java. That’s why Joda Time played a key role as a quality replacement for Java Date Time requirements.
Java 8 Date Time API
Java 8 Date Time API is JSR-310 implementation. It is designed to overcome all the flaws in the legacy date time implementations. Some of the design principles of new Date Time API are:
- Immutability: All the classes in the new Date Time API are immutable and good for multithreaded environments.
- Separation of Concerns: The new API separates clearly between human readable date time and machine time (unix timestamp). It defines separate classes for Date, Time, DateTime, Timestamp, Timezone etc.
- Clarity: The methods are clearly defined and perform the same action in all the classes. For example, to get the current instance we have
now()
method. There are format() and parse() methods defined in all these classes rather than having a separate class for them.All the classes use Factory Pattern and Strategy Pattern for better handling. Once you have used the methods in one of the class, working with other classes won’t be hard.
- Utility operations: All the new Date Time API classes comes with methods to perform common tasks, such as plus, minus, format, parsing, getting separate part in date/time etc.
- Extendable: The new Date Time API works on ISO-8601 calendar system but we can use it with other non ISO calendars as well.
Java Date Time API Packages
Java Date Time API consists of following packages.
- java.time Package: This is the base package of new Java Date Time API. All the major base classes are part of this package, such as
LocalDate
,LocalTime
,LocalDateTime
,Instant
,Period
,Duration
etc. All of these classes are immutable and thread safe. Most of the times, these classes will be sufficient for handling common requirements. - java.time.chrono Package: This package defines generic APIs for non ISO calendar systems. We can extend
AbstractChronology
class to create our own calendar system. - java.time.format Package: This package contains classes used for formatting and parsing date time objects. Most of the times, we would not be directly using them because principle classes in java.time package provide formatting and parsing methods.
- java.time.temporal Package: This package contains temporal objects and we can use it for find out specific date or time related to date/time object. For example, we can use these to find out the first or last day of the month. You can identify these methods easily because they always have format “withXXX”.
- java.time.zone Package: This package contains classes for supporting different time zones and their rules.
Java Date Time API Examples
We have looked into most of the important parts of Java Date Time API. It’s time now to look into most important classes of Date Time API with examples.
- java.time.LocalDate:
LocalDate
is an immutable class that represents Date with default format of yyyy-MM-dd. We can usenow()
method to get the current date. We can also provide input arguments for year, month and date to create LocalDate instance. This class provides overloaded method for now() where we can pass ZoneId for getting date in specific time zone. This class provides the same functionality asjava.sql.Date
. Let’s look at a simple example for it’s usage.package com.journaldev.java8.time; import java.time.LocalDate;
import java.time.Month;
import java.time.ZoneId; /**
* LocalDate Examples
* @author pankaj
*
*/
public class LocalDateExample { public static void main(String[] args) { //Current Date
LocalDate today = LocalDate.now();
System.out.println("Current Date="+today); //Creating LocalDate by providing input arguments
LocalDate firstDay_2014 = LocalDate.of(2014, Month.JANUARY, 1);
System.out.println("Specific Date="+firstDay_2014); //Try creating date by providing invalid inputs
//LocalDate feb29_2014 = LocalDate.of(2014, Month.FEBRUARY, 29);
//Exception in thread "main" java.time.DateTimeException:
//Invalid date 'February 29' as '2014' is not a leap year //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc
LocalDate todayKolkata = LocalDate.now(ZoneId.of("Asia/Kolkata"));
System.out.println("Current Date in IST="+todayKolkata); //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST
//LocalDate todayIST = LocalDate.now(ZoneId.of("IST")); //Getting date from the base date i.e 01/01/1970
LocalDate dateFromBase = LocalDate.ofEpochDay(365);
System.out.println("365th day from base date= "+dateFromBase); LocalDate hundredDay2014 = LocalDate.ofYearDay(2014, 100);
System.out.println("100th day of 2014="+hundredDay2014);
} }The example methods explanation is provided in comments, when we run this program, we get following output.
Current Date=2014-04-28
Specific Date=2014-01-01
Current Date in IST=2014-04-29
365th day from base date= 1971-01-01
100th day of 2014=2014-04-10 - java.time.LocalTime: LocalTime is an immutable class whose instance represents a time in the human readable format. It’s default format is hh:mm:ss.zzz. Just like LocalDate, this class provides time zone support and creating instance by passing hour, minute and second as input arguments. Let’s look at it’s usage with a simple program.
package com.journaldev.java8.time; import java.time.LocalTime;
import java.time.ZoneId; /**
* LocalTime Examples
* @author pankaj
*
*/
public class LocalTimeExample { public static void main(String[] args) { //Current Time
LocalTime time = LocalTime.now();
System.out.println("Current Time="+time); //Creating LocalTime by providing input arguments
LocalTime specificTime = LocalTime.of(12,20,25,40);
System.out.println("Specific Time of Day="+specificTime); //Try creating time by providing invalid inputs
//LocalTime invalidTime = LocalTime.of(25,20);
//Exception in thread "main" java.time.DateTimeException:
//Invalid value for HourOfDay (valid values 0 - 23): 25 //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc
LocalTime timeKolkata = LocalTime.now(ZoneId.of("Asia/Kolkata"));
System.out.println("Current Time in IST="+timeKolkata); //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST
//LocalTime todayIST = LocalTime.now(ZoneId.of("IST")); //Getting date from the base date i.e 01/01/1970
LocalTime specificSecondTime = LocalTime.ofSecondOfDay(10000);
System.out.println("10000th second time= "+specificSecondTime); } }When we run above program, we get following output.
Current Time=15:51:45.240
Specific Time of Day=12:20:25.000000040
Current Time in IST=04:21:45.276
10000th second time= 02:46:40 - java.time.LocalDateTime:
LocalDateTime
is an immutable date-time object that represents a date-time, with default format as yyyy-MM-dd-HH-mm-ss.zzz. It provides a factory method that takesLocalDate
andLocalTime
input arguments to createLocalDateTime
instance. Let’s look it’s usage with a simple example.package com.journaldev.java8.time; import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Month;
import java.time.ZoneId;
import java.time.ZoneOffset; public class LocalDateTimeExample { public static void main(String[] args) { //Current Date
LocalDateTime today = LocalDateTime.now();
System.out.println("Current DateTime="+today); //Current Date using LocalDate and LocalTime
today = LocalDateTime.of(LocalDate.now(), LocalTime.now());
System.out.println("Current DateTime="+today); //Creating LocalDateTime by providing input arguments
LocalDateTime specificDate = LocalDateTime.of(2014, Month.JANUARY, 1, 10, 10, 30);
System.out.println("Specific Date="+specificDate); //Try creating date by providing invalid inputs
//LocalDateTime feb29_2014 = LocalDateTime.of(2014, Month.FEBRUARY, 28, 25,1,1);
//Exception in thread "main" java.time.DateTimeException:
//Invalid value for HourOfDay (valid values 0 - 23): 25 //Current date in "Asia/Kolkata", you can get it from ZoneId javadoc
LocalDateTime todayKolkata = LocalDateTime.now(ZoneId.of("Asia/Kolkata"));
System.out.println("Current Date in IST="+todayKolkata); //java.time.zone.ZoneRulesException: Unknown time-zone ID: IST
//LocalDateTime todayIST = LocalDateTime.now(ZoneId.of("IST")); //Getting date from the base date i.e 01/01/1970
LocalDateTime dateFromBase = LocalDateTime.ofEpochSecond(10000, 0, ZoneOffset.UTC);
System.out.println("10000th second time from 01/01/1970= "+dateFromBase); } }In all the three examples, we have seen that if we provide invalid arguments for creating Date/Time, then it throws
java.time.DateTimeException
that is a RuntimeException, so we don’t need to explicitly catch it.
We have also seen that we can get Date/Time data by passing
ZoneId
, you can get the list of supported ZoneId values from it’s javadoc. When we run above class, we get following output.Current DateTime=2014-04-28T16:00:49.455
Current DateTime=2014-04-28T16:00:49.493
Specific Date=2014-01-01T10:10:30
Current Date in IST=2014-04-29T04:30:49.493
10000th second time from 01/01/1970= 1970-01-01T02:46:40- java.time.Instant: Instant class is used to work with machine readable time format, it stores date time in unix timestamp. Let’s see it’s usage with a simple program.
package com.journaldev.java8.time; import java.time.Duration;
import java.time.Instant; public class InstantExample { public static void main(String[] args) {
//Current timestamp
Instant timestamp = Instant.now();
System.out.println("Current Timestamp = "+timestamp); //Instant from timestamp
Instant specificTime = Instant.ofEpochMilli(timestamp.toEpochMilli());
System.out.println("Specific Time = "+specificTime); //Duration example
Duration thirtyDay = Duration.ofDays(30);
System.out.println(thirtyDay);
} }Output of above program is:
Current Timestamp = 2014-04-28T23:20:08.489Z
Specific Time = 2014-04-28T23:20:08.489Z
PT720H - Date API Utilities: As mentioned earlier, most of the Date Time principle classes provide various utility methods such as plus/minus days, weeks, months etc. There are some other utility methods for adjusting the date using
TemporalAdjuster
and to calculate the period between two dates.package com.journaldev.java8.time; import java.time.LocalDate;
import java.time.LocalTime;
import java.time.Period;
import java.time.temporal.TemporalAdjusters; public class DateAPIUtilities { public static void main(String[] args) { LocalDate today = LocalDate.now(); //Get the Year, check if it's leap year
System.out.println("Year "+today.getYear()+" is Leap Year? "+today.isLeapYear()); //Compare two LocalDate for before and after
System.out.println("Today is before 01/01/2015? "+today.isBefore(LocalDate.of(2015,1,1))); //Create LocalDateTime from LocalDate
System.out.println("Current Time="+today.atTime(LocalTime.now())); //plus and minus operations
System.out.println("10 days after today will be "+today.plusDays(10));
System.out.println("3 weeks after today will be "+today.plusWeeks(3));
System.out.println("20 months after today will be "+today.plusMonths(20)); System.out.println("10 days before today will be "+today.minusDays(10));
System.out.println("3 weeks before today will be "+today.minusWeeks(3));
System.out.println("20 months before today will be "+today.minusMonths(20)); //Temporal adjusters for adjusting the dates
System.out.println("First date of this month= "+today.with(TemporalAdjusters.firstDayOfMonth()));
LocalDate lastDayOfYear = today.with(TemporalAdjusters.lastDayOfYear());
System.out.println("Last date of this year= "+lastDayOfYear); Period period = today.until(lastDayOfYear);
System.out.println("Period Format= "+period);
System.out.println("Months remaining in the year= "+period.getMonths());
}
}Output of above program is:
Year 2014 is Leap Year? false
Today is before 01/01/2015? true
Current Time=2014-04-28T16:23:53.154
10 days after today will be 2014-05-08
3 weeks after today will be 2014-05-19
20 months after today will be 2015-12-28
10 days before today will be 2014-04-18
3 weeks before today will be 2014-04-07
20 months before today will be 2012-08-28
First date of this month= 2014-04-01
Last date of this year= 2014-12-31
Period Format= P8M3D
Months remaining in the year= 8 - Parsing and Formatting: It’s very common to format date into different formats and then parse a String to get the Date Time objects. Let’s see it with simple examples.
package com.journaldev.java8.time; import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter; public class DateParseFormatExample { public static void main(String[] args) { //Format examples
LocalDate date = LocalDate.now();
//default format
System.out.println("Default format of LocalDate="+date);
//specific format
System.out.println(date.format(DateTimeFormatter.ofPattern("d::MMM::uuuu")));
System.out.println(date.format(DateTimeFormatter.BASIC_ISO_DATE)); LocalDateTime dateTime = LocalDateTime.now();
//default format
System.out.println("Default format of LocalDateTime="+dateTime);
//specific format
System.out.println(dateTime.format(DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss")));
System.out.println(dateTime.format(DateTimeFormatter.BASIC_ISO_DATE)); Instant timestamp = Instant.now();
//default format
System.out.println("Default format of Instant="+timestamp); //Parse examples
LocalDateTime dt = LocalDateTime.parse("27::Apr::2014 21::39::48",
DateTimeFormatter.ofPattern("d::MMM::uuuu HH::mm::ss"));
System.out.println("Default format after parsing = "+dt);
} }When we run above program, we get following output.
Default format of LocalDate=2014-04-28
28::Apr::2014
20140428
Default format of LocalDateTime=2014-04-28T16:25:49.341
28::Apr::2014 16::25::49
20140428
Default format of Instant=2014-04-28T23:25:49.342Z
Default format after parsing = 2014-04-27T21:39:48 - Legacy Date Time Support: Legacy Date/Time classes are used in almost all the applications, so having backward compatibility is a must. That’s why there are several utility methods through which we can convert Legacy classes to new classes and vice versa. Let’s see this with a simple example.
package com.journaldev.java8.time; import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.TimeZone; public class DateAPILegacySupport { public static void main(String[] args) { //Date to Instant
Instant timestamp = new Date().toInstant();
//Now we can convert Instant to LocalDateTime or other similar classes
LocalDateTime date = LocalDateTime.ofInstant(timestamp,
ZoneId.of(ZoneId.SHORT_IDS.get("PST")));
System.out.println("Date = "+date); //Calendar to Instant
Instant time = Calendar.getInstance().toInstant();
System.out.println(time);
//TimeZone to ZoneId
ZoneId defaultZone = TimeZone.getDefault().toZoneId();
System.out.println(defaultZone); //ZonedDateTime from specific Calendar
ZonedDateTime gregorianCalendarDateTime = new GregorianCalendar().toZonedDateTime();
System.out.println(gregorianCalendarDateTime); //Date API to Legacy classes
Date dt = Date.from(Instant.now());
System.out.println(dt); TimeZone tz = TimeZone.getTimeZone(defaultZone);
System.out.println(tz); GregorianCalendar gc = GregorianCalendar.from(gregorianCalendarDateTime);
System.out.println(gc); } }When we run above application, we get following output.
Date = 2014-04-28T16:28:54.340
2014-04-28T23:28:54.395Z
America/Los_Angeles
2014-04-28T16:28:54.404-07:00[America/Los_Angeles]
Mon Apr 28 16:28:54 PDT 2014
sun.util.calendar.ZoneInfo[id="America/Los_Angeles",offset=-28800000,dstSavings=3600000,useDaylight=true,transitions=185,lastRule=java.util.SimpleTimeZone[id=America/Los_Angeles,offset=-28800000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]]
java.util.GregorianCalendar[time=1398727734404,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/Los_Angeles",offset=-28800000,dstSavings=3600000,useDaylight=true,transitions=185,lastRule=java.util.SimpleTimeZone[id=America/Los_Angeles,offset=-28800000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2014,MONTH=3,WEEK_OF_YEAR=18,WEEK_OF_MONTH=5,DAY_OF_MONTH=28,DAY_OF_YEAR=118,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=4,AM_PM=1,HOUR=4,HOUR_OF_DAY=16,MINUTE=28,SECOND=54,MILLISECOND=404,ZONE_OFFSET=-28800000,DST_OFFSET=3600000]As you can see that legacy
TimeZone
andGregorianCalendar
classes toString() methods are too verbose and not user friendly.
That’s all for Java 8 Date Time API, I like this new API a lot. It’s very easy to work with and having similar methods that does a particular job makes it easy to find. It will take some time from moving legacy classes to new Date Time classes, but I believe it will be worthy of the time.
Java 8 Date Time API Example Tutorial – LocalDate, Instant, LocalDateTime, Parse and Format的更多相关文章
- Java之Date Time API (Java 8 新特性)
Java 8 – Date Time API Java 8 comes with a much improved and much required change in the way date an ...
- [转载]Java 8 日期&时间 API
Java 8 日期和时间 声明 本文转自http://www.journaldev.com/2800/java-8-date-localdate-localdatetime-instant,以mark ...
- [转载]java中Date,SimpleDateFormat
一.Java中的日期概述: 日期在Java中是一块非常复杂的内容,对于一个日期在不同的语言国别环境中,日期的国际化,日期和时间之间的转换,日期的加减运算,日期的展示格式都是非常复杂的问题. 在Java ...
- java.util.Date与java.sql.Date
我数据库里用到了日期类型.用java编程的时候同时import了java.util.*和java.sql.*,发现直接申明Date类型 Date dt; 会报错,查了一下才发现有java.util.D ...
- [转]Java中Date转换大全,返回yyyy-MM-dd的Date类型
/** * 获取现在时间,这个好用 * * @return返回长时间格式 yyyy-MM-dd HH:mm:ss */ public static Date getSqlDate() { Date s ...
- java.util.Date和jdk1.8新时间API比拼
旧的时间和日期的API的缺陷 Java 的 java.util.Date 和 java.util.Calendar 类易用性差,不支持时区,而且都不是线程安全的. Date如果不格式化,打印出的日期可 ...
- Java日期时间API系列8-----Jdk8中java.time包中的新的日期时间API类的LocalDate源码分析
目录 0.前言 1.TemporalAccessor源码 2.Temporal源码 3.TemporalAdjuster源码 4.ChronoLocalDate源码 5.LocalDate源码 6.总 ...
- 【spring mvc】后台API查询接口,get请求,后台Date字段接收前台String类型的时间,报错default message [Failed to convert property value of type 'java.lang.String' to required type 'java.util.Date' for property 'createDate';
后台API查询接口,get请求,后台Date字段接收前台String类型的时间筛选条件 后台接口接收 使用的实体 而createDate字段在后台实体中是Date类型 报错信息: org.spring ...
- Spring Boot和Feign中使用Java 8时间日期API(LocalDate等)的序列化问题【转】
Spring Boot和Feign中使用Java 8时间日期API(LocalDate等)的序列化问题 http://blog.didispace.com/Spring-Boot-And-Feign- ...
随机推荐
- [Bhatia.Matrix Analysis.Solutions to Exercises and Problems]ExI.3.1
Let $A=A_1\oplus A_2$. Show that (1). $W(A)$ is the convex hull of $W(A_1)$ and $W(A_2)$; i.e., the ...
- QTP、LoadRunner、QC工具下载地址
QTP10.0工具下载地址:http://h30302.www3.hp.com/prdownloads/T6510-15063.zip?ordernumber=380454070&itemid ...
- fedora下的dropbox
- VirtualBox Headless启动虚拟机
习惯了在Windows上来学习和娱乐,所以不能切换到Linux系统. 为了Linux编程,我首先尝试了wubi在Windows上安装双系统,但是发现本来启动很快的Windows8安装了双系统之后,系统 ...
- 2015长春 HDU 5534 Partial Tree
题意:有n个结点,n-1条边,现在要把这n个结点连成一棵树,给定了f(i),表示度为i的结点的价值是f(i).现在问如何连能够使得Σf(i)的值最大. 思路:每个点至少一个度,所以可分配的度数为n-2 ...
- android sdk api结构解析
一.系统级:android.accounts android.app 1.OS 相关 android.os android.os.storage ...
- Android Binder------ServiceManager启动分析
ServiceManager启动分析 简述: ServiceManager是一个全局的manager.调用了Jni函数,实现addServicew getService checkService ...
- 单点登录与消息队列以及在J2EE中的实现方案
前言 这次为大家简单介绍两个在WEB开发中经常使用的概念——单点登录和消息队列以及具体到J2EE中的一些实现方案.本文原创性的工作比较少,主要是一些总结概括和自己的理解. 单点登录SSO SSO的业务 ...
- Spark生态之Spark BlinkDB
- Android实例-OrientationSensor方向传感器(XE8+小米2)
相关资料: <修复 XE8 for Android 方向传感器 headingX,Y,Z 不会动的问题>:http://www.cnblogs.com/onechen/p/4497282. ...