I come from the C# world, so not too experience开发者_Python百科d 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?

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

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 & 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, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

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. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
  • Java 9 brought some minor features and fixes.
• Java SE 6 and Java SE 7
  • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android (26+) bundle implementations of the java.time classes.
  • For earlier Android (<26), the latest Android tooling enables a process known as API desugaring to provide a subset of the java.time functionality not originally built into Android.
    • If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

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.

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.

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.

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 & jdk7)

Date itself is not deprecated. It's just a lot of its methods are. See here for details.

Use java.util.Calendar instead.

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

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.

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));

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

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

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.

new GregorianCalendar(1985, Calendar.JANUARY, 1).getTime();

(the pre-Java-8 way)