Is there a Java equivalent of DateTime.MinValue and DateTime.Today in the Java Date class? Or a way of achieving something similar?

I've realised how spoilt you are with the .NET datetime cla开发者_如何学Goss, I also need the equivalent of AddDays(), AddMonths().

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The de-facto Java datetime API is joda-time.

With it, you can get the current date/time by just constructing new DateTime().

Similarly, Without it, you can use Calendar.getInstance() or new Date() to obtain the current date/time.

MinValue can be Calendar.getInstance(0) / new Date(0). This would use the default chronology - i.e. since January 1st, 1970. Since MinValue returns Januar 1st, year 1, you can do that be simply specifying this date, using the appropriate constructor of DateTime.

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The other Answers may be correct but use outmoded classes.

java.time

The old date-time classes (java.util.Date/.Calendar etc.) were supplanted by Joda-Time, which in turn has been supplanted by the java.time framework built into Java 8 and later. The java.time classes are inspired by Joda-Time, defined by JSR 310, extended by the ThreeTen-Extra project, back-ported to Java 6 & 7 by the ThreeTen-Backport project, and adapted to Android in the ThreeTenABP project. See Tutorial.

To get the current moment on the timeline in UTC with a resolution of nanoseconds, use Instant.

Instant now = Instant.now();

Instant has three constants:

• EPOCH – 1970-01-01T00:00:00Z
• MIN – -1000000000-01-01T00:00Z
• MAX – 1000000000-12-31T23:59:59.999999999Z

To get the current moment for an offset-from-UTC, apply a ZoneOffset to get an OffsetDateTime.

OffsetDateTime now = OffsetDateTime.now( ZoneOffset.of( "-04:00" ) );

Better to apply a full time zone (offset plus rules for anomalies such as Daylight Saving Time) if known. Apply a ZoneId to get a ZonedDateTime.

ZonedDateTime now = ZonedDateTime.now( ZoneId.of( "America/Montreal" ) );

You can perform arithmetic.

ZonedDateTime dayLater = now.plusDays( 1 );
ZonedDateTime monthLater = now.plusMonths( 1 );

You can get the first moment of a day.

ZoneId zoneId = ZoneId.of( "America/Montreal" );
ZonedDateTime tomorrowStart = now.toLocalDate().atStartOfDay( zoneId );  // Usually time-of-day of `00:00:00.0` but not always.

If you need only a date without time-of-day and without time zone, use LocalDate. Similarly, LocalTime for time-only without date and without time zone. Usually better to stick with Instant and OffsetDateTime/ZonedDateTime as the Local… types do not represent actual moments on the timeline (no offset or time zone means they are undefined).

LocalDate localDate = LocalDate.now( zoneId );
LocalTime localTime = LocalTime.now( zoneId );

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Comparison of Date/Time features in .NET and Java

.NET DateTime (C#)	Joda DateTime (Java, deprecated) [See Note #2]	Java Date
DateTime.MinValue	new DateTime(Long.MIN_VALUE)	new Date(Long.MIN_VALUE) [See Note #3]
DateTime.Today	new DateTime().withTimeAtStartOfDay()	Messy [See Note #4]
DateTime.Now	new DateTime()	new Date()
DateTime.MaxValue	new DateTime(Long.MAX_VALUE)	new Date(Long.MAX_VALUE)

Additional notes:

1. Dealing with dates and times is messy. This table is intended to be a starting point for code migrations. The comparisons compare concepts, not exact values (e.g. .NET's minimum date/time is not the same value as Java's)
2. Joda DateTime is the preferred date/time library for Java.
3. See additional notes on new Date(Long.MIN_VALUE) in Java
4. Getting start of day with Java's Date is a little more involved - see here.
5. .NET DateTimes default to local date/time, whereas in Java they default to UTC. Make sure to consider any impact of timezones when working with dates and times.

Joda-Time Deprecated

Joda-Time is deprecated. From their web-site ^archive:

Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.

Meaning that java.util.Date → org.joda.time.DateTime → java.time.ZonedDateTime

Giving us new mappings:

.NET DateTime (C#)	java.time (formerly known as Joda-Time)	Java Date
DateTime.MinValue	LocalDateTime.MIN	new Date(Long.MIN_VALUE)
DateTime.Today	LocalDateTime.of(LocalDate.NOW, LocalTime.MIDNIGHT)	(not available)
DateTime.Now	LocalDateTime.now()	new Date()
DateTime.UtcNow	LocalDateTime.now(ZoneOffset.UTC)	(not available)
DateTime.MaxValue	LocalDateTime.MAX	new Date(Long.MAX_VALUE)

The .NET DateTime contains:

• date
• time
• and no particular information about what timezone it contains (except to day "Local", "UTC", or "Unspecified").

This means the java.time equivalent is LocalDateTime. If you want a datetime object that also carries with it an offset from UTC:

• .NET: DateTimeOffset
• java.time: ZonedDateTime

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Most date manipulation should be done using the Calendar object now.

http://download.oracle.com/javase/6/docs/api/java/util/Calendar.html

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to get the current date:

Calendar calendar = Calendar.getInstance(); SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");

    try {

        System.out.println("Today: " + dateFormat.format(calendar.getTime()));

    } catch (Exception e) {
        e.printStackTrace();
    }

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Theres calendar http://download.oracle.com/javase/1.5.0/docs/api/java/util/Calendar.html

And date http://download.oracle.com/javase/1.4.2/docs/api/java/util/Date.html

Theres also simpledateformat for formatting. http://download.oracle.com/javase/1.4.2/docs/api/java/text/SimpleDateFormat.html