tl;dr
Should I use java.util.Date or java.sql.Date?
Neither.
Both are obsolete as of JDBC 4.2 and later. Use java.time classes instead.
- date-only value
For a database type akin to SQL-standard DATE, use java.time.LocalDate.
LocalDate ld = myResultSet.getObject( … , LocalDate.class ) ;myPreparedStatement.setObject( ld , … ) ;
- date with time-of-day in UTC value
For a database type akin to SQL-standard TIMESTAMP WITH TIME ZONE, use java.time.Instant.
Instant instant = myResultSet.getObject( … , Instant.class ) ;myPreparedStatement.setObject( instant , … ) ;
Details
The question and other answers seem to be over-thinking the issue. A java.sql.Date is merely a java.util.Date with its time set to 00:00:00.
From the java.sql.Date doc (italicized text is mine)…
Class Date
java.lang.Object
????java.util.Date????????← Inherits from j.u.Date
????????java.sql.Date
…
A thin wrapper around a millisecond value that allows JDBC to identify this as an SQL DATE value. A milliseconds value represents the number of milliseconds that have passed since January 1, 1970 00:00:00.000 GMT.??← Time-of-day set to Zero, midnight GMT/UTC
To conform with the definition of SQL DATE, the millisecond values wrapped by a java.sql.Date instance must be 'normalized' by setting the hours, minutes, seconds, and milliseconds to zero in the particular time zone with which the instance is associated.
Date-Only versus Date-Time
The core problem is:
- SQL
In SQL, the DATE data type stores a date-only, without a time-of-day.
- JAVA
In the badly designed date-time library bundled with the early versions of Java, they failed to include a class to represent a date-only.
Instead of creating a date-only class, the Java team made a terrible hack. They took their date-time class (the misnamed java.util.Date class, containing both date and time) and extended it to have an instance set its time-of-day to midnight UTC, 00:00:00. That hack, that subclass of j.u.Date, is java.sql.Date.
All this hacking, poor design, and misnaming has made a confusing mess.
Which To Use
So when to use which? Simple, after cutting through the confusion.
- When reading or writing to a database’s date-only column, use
java.sql.Date as it clumsily tries to mask its time-of-day.
- Everywhere else in Java, where you need a time-of-day along with your date, use
java.util.Date.
- When you have a java.sql.Date in hand but need a java.util.Date, simply pass the java.sql.Date. As a subclass, a java.sql.Date is a java.util.Date.
Even Better
In modern Java, you now have a choice of decent date-time libraries to supplant the old and notoriously troublesome java.util.Date, Calendar, SimpleTextFormat, and java.sql.Date classes bundled with Java. The main choices are:
Both offer a LocalDate class to represent a date only, with no time-of-day and no time zone.
A JDBC driver updated to JDBC 4.2 or later can be used to directly exchange java.time objects with the database. Then we can completely abandon the ugly mess that is the date-time classes in the java.util.* and java.sql.* packages.
setObject | getObject
This article published by Oracle explains that the JDBC in Java 8 has been updated transparently to map a SQL DATE value to the new java.time.LocalDate type if you call getObject and setObject methods.
In obtuse language, the bottom of the JDBC 4.2 update spec confirms that article, with new mappings added to the getObject and setObject methods.
myPreparedStatement.setObject( … , myLocalDate ) ;
…and…
LocalDate myLocalDate = myResultSet.getObject( … , LocalDate.class ) ;
Convert
The spec also says new methods have been added to the java.sql.Date class to convert back and forth to java.time.LocalDate.
Time Zone
The old java.util.Date, java.sql.Date, and java.sql.Timestamp are always in UTC. The first two (at least) have a time zone buried deep in their source code but is used only under-the-surface such as the equals method, and has no getter/setter.
More confusingly, their toString methods apply the JVM’s current default time zone. So to the na?ve programmer it seems like they have a time zone but they do not.
Both the buried time zone and the toString behavior are two of many reasons to avoid these troublesome old legacy classes.
Write your business logic using java.time (Java 8 and later). Where java.time lacks, use Joda-Time. Both java.time and Joda-Time have convenient methods for going back and forth with the old classes where need be.
Replacements:
The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).
All three java.time.Local… classes are all lacking any concept of time zone or offset-from-UTC.
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?
