Java Why is the Date constructor deprecated and what do I use instead

Question

I come from the C  world  so not too experienced with Java yet  I was just told by Eclipse that Date was deprecated   Person p   new Person    p setDateOfBirth new Date 1985  1  1      Why  And what  especially in cases like above  should be used instead

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You can make a method just like new Date year month date  in your code by using Calendar class    private Date getDate int year int month int date       Calendar cal   Calendar getInstance        cal set Calendar YEAR  year       cal set Calendar MONTH  month-1       cal set Calendar DAY OF MONTH  day       return cal getTime        It will work just like the deprecated constructor of Date

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Most Java developers currently use the third party package Joda-Time  It is widely regarded to be a much better implementation  Java 8 however will have a new java time   package  See this article  Introducing the New Date and Time API for JDK 8

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I got this from Secure Code Guideline for Java  The examples in this section use java util Date extensively as it is an example of a mutable API class  In an application  it would be preferable to use the new Java Date and Time API  java time    which has been designed to be immutable

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The specific Date constructor is deprecated  and Calendar should be used instead   The JavaDoc for Date describes which constructors are deprecated and how to replace them using a Calendar

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tl dr  LocalDate of  1985   1   1        or     LocalDate of  1985   Month JANUARY   1     Details  The java util Date  java util Calendar  and java text SimpleDateFormat classes were rushed too quickly when Java first launched and evolved  The classes were not well designed or implemented  Improvements were attempted  thus the deprecations you   ve found  Unfortunately the attempts at improvement largely failed  You should avoid these classes altogether  They are supplanted in Java 8 by new classes   Problems In Your Code  A java util Date has both a date and a time portion  You ignored the time portion in your code  So the Date class will take the beginning of the day as defined by your JVM   s default time zone and apply that time to the Date object  So the results of your code will vary depending on which machine it runs or which time zone is set  Probably not what you want   If you want just the date  without the time portion  such as for a birth date  you may not want to use a Date object  You may want to store just a string of the date  in ISO 8601 format of YYYY-MM-DD  Or use a LocalDate object from Joda-Time  see below    Joda-Time  First thing to learn in Java  Avoid the notoriously troublesome java util Date  amp  java util Calendar classes bundled with Java    As correctly noted in the answer by user3277382  use either Joda-Time or the new java time   package in Java 8   Example Code in Joda-Time 2 3  DateTimeZone timeZoneNorway   DateTimeZone forID   Europe Oslo     DateTime birthDateTime InNorway   new DateTime  1985  1  1  3  2  1  timeZoneNorway     DateTimeZone timeZoneNewYork   DateTimeZone forID   America New York     DateTime birthDateTime InNewYork   birthDateTime InNorway toDateTime  timeZoneNewYork      DateTime birthDateTime UtcGmt   birthDateTime InNorway toDateTime  DateTimeZone UTC     LocalDate birthDate   new LocalDate  1985  1  1      Dump to console     System out println   birthDateTime InNorway      birthDateTime InNorway    System out println   birthDateTime InNewYork      birthDateTime InNewYork    System out println   birthDateTime UtcGmt      birthDateTime UtcGmt    System out println   birthDate      birthDate      When run     birthDateTime InNorway  1985-01-01T03 02 01 000 01 00 birthDateTime InNewYork  1984-12-31T21 02 01 000-05 00 birthDateTime UtcGmt  1985-01-01T02 02 01 000Z birthDate  1985-01-01   java time  In this case the code for java time is nearly identical to that of Joda-Time    We get a time zone  ZoneId   and construct a date-time object assigned to that time zone  ZonedDateTime   Then using the Immutable Objects pattern  we create new date-times based on the old object   s same instant  count of nanoseconds since epoch  but assigned other time zone  Lastly we get a LocalDate which has no time-of-day nor time zone though notice the time zone applies when determining that date  a new day dawns earlier in Oslo than in New York for example    ZoneId zoneId Norway   ZoneId of   Europe Oslo     ZonedDateTime zdt Norway   ZonedDateTime of  1985   1   1   3   2   1   0   zoneId Norway     ZoneId zoneId NewYork   ZonedId of   America New York     ZonedDateTime zdt NewYork   zdt Norway withZoneSameInstant  zoneId NewYork     ZonedDateTime zdt Utc   zdt Norway withZoneSameInstant  ZoneOffset UTC        Or  next line is similar  Instant instant   zdt Norway toInstant        Instant is always in UTC   LocalDate localDate Norway   zdt Norway toLocalDate        About java time  The java time framework is built into Java 8 and later  These classes supplant the troublesome old legacy date-time classes such as java util Date  Calendar   amp  SimpleDateFormat   The Joda-Time project  now in maintenance mode  advises migration to the java time classes   To learn more  see the Oracle Tutorial  And search Stack Overflow for many examples and explanations  Specification is JSR 310   You may exchange java time objects directly with your database  Use a JDBC driver compliant with JDBC 4 2 or later  No need for strings  no need for java sql   classes   Where to obtain the java time classes     Java SE 8  Java SE 9  Java SE 10  and later   Built-in   Part of the standard Java API with a bundled implementation  Java 9 adds some minor features and fixes   Java SE 6 and Java SE 7   Much of the java time functionality is back-ported to Java 6  amp  7 in ThreeTen-Backport   Android   Later versions of Android bundle implementations of the java time classes  For earlier Android   lt 26   the ThreeTenABP project adapts ThreeTen-Backport  mentioned above   See How to use ThreeTenABP        The ThreeTen-Extra project extends java time with additional classes  This project is a proving ground for possible future additions to java time  You may find some useful classes here such as Interval  YearWeek  YearQuarter  and more

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new GregorianCalendar 1985  Calendar JANUARY  1  getTime       the pre-Java-8 way

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Similar to what binnyb suggested  you might consider using the newer Calendar   GregorianCalendar method  See these more recent docs   http   download oracle com javase 6 docs api java util GregorianCalendar html

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One reason that the constructor is deprecated is that the meaning of the year parameter is not what you would expect   The javadoc says      As of JDK version 1 1  replaced by Calendar set year   1900  month  date     Notice that the year field is the number of years since 1900  so your sample code most likely won t do what you expect it to do   And that s the point   In general  the Date API only supports the modern western calendar  has idiosyncratically specified components  and behaves inconsistently if you set fields   The Calendar and GregorianCalendar APIs are better than Date  and the 3rd-party Joda-time APIs were generally thought to be the best   In Java 8  they introduced the java time packages  and these are now the recommended alternative

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The java util Date class isn t actually deprecated  just that constructor  along with a couple other constructors methods are deprecated  It was deprecated because that sort of usage doesn t work well with internationalization  The Calendar class should be used instead   Calendar cal   Calendar getInstance    cal set Calendar YEAR  1988   cal set Calendar MONTH  Calendar JANUARY   cal set Calendar DAY OF MONTH  1   Date dateRepresentation   cal getTime      Take a look at the date Javadoc   http   download oracle com javase 6 docs api java util Date html

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I came across this question as a duplicate of a newer question which asked what the non-deprecated way to get a Date at a specific year  month  and day was   The answers here so far say to use the Calendar class  and that was true until Java 8 came out  But as of Java 8  the standard way to do this is   LocalDate localDate   LocalDate of 1985  1  1     And then if you really really need a java util Date  you can use the suggestions in this question   For more info  check out the API or the tutorials for Java 8

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The Date constructor expects years in the format of years since 1900  zero-based months  one-based days  and sets hours minutes seconds milliseconds to zero   Date result   new Date year  month  day     So using the Calendar replacement  zero-based years  zero-based months  one-based days  for the deprecated Date constructor  we need something like   Calendar calendar   Calendar getInstance    calendar clear       Sets hours minutes seconds milliseconds to zero calendar set year   1900  month  day   Date result   calendar getTime      Or using Java 1 8  which has zero-based year  and one-based months and days    Date result   Date from LocalDate of year   1900  month   1  day  atStartOfDay ZoneId systemDefault    toInstant       Here are equal versions of Date  Calendar  and Java 1 8   int year   1985     1985 int month   1     January int day   1     1st     Original  1900-based year  zero-based month  one-based day Date date1   new Date year - 1900  month - 1  day       Calendar  zero-based year  zero-based month  one-based day Calendar calendar   Calendar getInstance    calendar clear       Sets hours minutes seconds milliseconds to zero calendar set year  month - 1  day   Date date2   calendar getTime        Java-time back to Date  zero-based year  one-based month  one-based day Date date3   Date from LocalDate of year  month  day  atStartOfDay ZoneId systemDefault    toInstant      SimpleDateFormat format   new SimpleDateFormat  yyyy-MMM-dd HH mm ss SSS        All 3 print  1985-Jan-01 00 00 00 000  System out println format format date1    System out println format format date2    System out println format format date3

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As the Date constructor is deprecated  you can try this code   import java util Calendar     Calendar calendar   Calendar getInstance         calendar set Calendar HOUR OF DAY  6     for 6 hour      calendar set Calendar MINUTE  0     for 0 min      calendar set Calendar SECOND  0     for 0 sec      calendar set 1996 0 26     for Date  year month 0 to 11   date       Date date   new Date calendar getTimeInMillis       calendar gives long value      String mConvertedDate   date toString      Fri Jan 26 06 00 00 GMT 05 30 1996

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Please note that Calendar getTime   is nondeterministic in the sense that the day time part defaults to the current time   To reproduce  try running following code a couple of times   Calendar c   Calendar getInstance    c set 2010  2  7      NB  2 means March  not February  System err println c getTime       Output eg    Sun Mar 07 10 46 21 CET 2010   Running the exact same code a couple of minutes later yields   Sun Mar 07 10 57 51 CET 2010   So  while set   forces corresponding fields to correct values  it leaks system time for the other fields   Tested above with Sun jdk6  amp  jdk7

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Date itself is not deprecated  It s just a lot of its methods are  See here for details   Use java util Calendar instead

[java] Java: Why is the Date constructor deprecated, and what do I use instead?

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