CODEWITHSUNDEEP
javadatejdbcsimpledateformat
Vaandu
Vaandu

Reputation: 4945

Date.toString() - sql vs util dates

I need to remove time from a Date Object. Here is my try,

Code:

System.out.println("date " + dbDate);
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
System.out.println("formatter.format(dbDate) " + formatter.format(dbDate));
System.out.println("final " + formatter.parse(formatter.format(dbDate)));

Output:

date 2011-12-03 23:59:59.0
formatter.format(dbDate) 2011-12-03
final Sat Dec 03 00:00:00 IST 2011

I want to the final date to display in 2011-12-03. But after conversion toString() of that Date is in different format. I am missing something. Please help.

Update:

In my application, I have two different methods to get dbDate. EXPIRY_DATE column is type of DATE.

First query uses dbDate = (java.util.Date) rs.getDate("EXPIRY_DATE");.

For this dbDate, System.out.println("date " + dbDate); gives date 2011-12-03

Second query uses dbDate = rs.getTimestamp("EXPIRY_DATE");

For this dbDate, System.out.println("date " + dbDate); gives date 2011-12-03 23:59:59.0.

This is my problem. As I thought toString() was giving problem, I didn't mention the full problem.

Solution:

I did not have choices to avoid java.sql.Date as my application methods have multiple usages. I tried the below and worked,

dbDate = new java.sql.Date(dbDate.getTime());

Upvotes: 1

Views: 5584

Answers (5)

Basil Bourque
Basil Bourque

Reputation: 340118

java.time

The Answer by BalusC is correct: You cannot eliminate a time-of-day from a class object defined to hold a date plus a time-of-day.

Also, you are using troublesome old classes (java.util.Date and java.sql.Date) that are now obsolete, supplanted by the java.time classes.

Instead, use a date-only class for a date-only value. The LocalDate class represents a date-only value without time-of-day and without time zone. The java.sql.Date pretends to do the same, but actually does carry a time of day due to very poor design decision of inheriting from java.util.Date. Avoid java.sql.Date, and use only java.time.LocalDate instead.

You are starting with a java.util.Date object apparently. That represents a point on the timeline in UTC with a resolution in milliseconds. So using that to determine a date requires a time zone. The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment, so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!). 

ZoneId z = ZoneId.of( "America/Montreal" ) ;

If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.

ZoneId z = ZoneId.systemDefault() ;  // Get JVM’s current default time zone.

To get a date-only value from your java.util.Date, first convert to its java.time replacement, Instant. To convert back and forth, call new methods added to the old classes.

Instant instant = myJavaUtilDate.toInstant() ;

That value is in UTC by definition. Apply your desired time zone (ZoneId) to generate a ZonedDateTime. 

ZonedDateTime zdt = instant.atZone( z ) ;

Finally, extract your desired LocalDate object from ZonedDateTime. 

LocalDate ld = zdt.toLocalDate() ;

As of JDBC 4.2 and later, you can directly exchange java.time classes with your database. So no need to use the the java.sql classes such as java.sql.Date and java.sql.Timestamp.

myPreparedStatement.setObject( … , ld ) ;

Retrieval.

LocalDate ld = myResultSet.getObject( … , LocalDate.class ) ;

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.

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?

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.

Upvotes: 0

Serhat Oz
Serhat Oz

Reputation: 798

I have encountered similar problem for those who encounters the same problem as mine I write this entry:

The problem is the date value that is taken from database and passed to the web client is in format yyyy-mm-dd but in the application for the first entry there is not database value so we create date object and passed the value to web client which gives us timestamp value. The value that will be passed to web client must be in date format so SimpleDateFormat is not a good choice for me So from this post ı understand the difference of java.sql.date and java.util.date and then create first object as

Date date = new java.sql.Date(1430454600000L);

which gives yyyy-mm-dd value for toString method.

Upvotes: 0

BalusC
BalusC

Reputation: 1109635

I need to remove time from a Date Object

You can't. The java.util.Date object contains both the date and time. Its toString() is also in a fixed format. If you want to represent it without time to humans, then you need to convert it to a String like as you already did. Or, if you intend to store it in the DB without the time (as the db part in the variable name dbDate suggests), then you need to convert it to java.sql.Date.

preparedStatement.setDate(1, new java.sql.Date(dbDate.getTime()));
// ...

Update as per your update, the ResultSet#getDate() returns an instance of java.sql.Date, not java.util.Date (but it is a subclass of java.util.Date, that's why the unnecessary cast worked; please note that casting is not the same as converting, a real conversion would be new java.util.Date(dbDate.getTime())). As you can read in the javadoc of the toString() method of java.sql.Date, it's indeed in yyyy-MM-dd format.

So, your concrete problem is that you're confusing java.sql.Date with java.util.Date and that you're misgrasping the internal workings of java.util.Date and been mislead by the toString() method. Everything is working as intented.

Related:

Upvotes: 5

Viruzzo
Viruzzo

Reputation: 3025

When you last call formatter.parse() you get back a Date object; the concatenation then makes an implicit call to Date.toString(): the format returned by this call is the default for the locale set in the JVM. What you must understand is that the Date object has no knowledge of the string representation, internally it's just an aggregate of inte

Upvotes: 0

Xavi López
Xavi López

Reputation: 27880

If what you want to do is remove the time part of the Date object:

If you only want to obtain a String representation without the time part of the Date object:

  • You've got to use SimpleDateFormat.format(). You can't make Date.toString() return a different value, it will always use that pattern. Look at its source code.

Upvotes: 1

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