在java中获得最大日期值的最佳方法？

Question

I'm writing a bit of logic that requires treating null dates as meaning forever in the future (the date in question is an expiration date, which may or may not exist). Instead of putting in special cases for a null date throughout the code, I want to just convert null into the maximum possible Date. I don't see any obvious ways to get such a value without hard coding it. What's the best way to get the maximum value of whatever Date implementation is being used?

Answer 1

Try

new Date(Long.MAX_VALUE)

which should give you the longest possible date value in Java.

Answer 2

Encapsulate the functionality you want in your own class, using Long.MAX_VALUE will most likely cause you problems.

class ExpirationDate {
    Date expires;

    boolean hasExpiration() {
        return expires == null;
    }

    Date getExpirationDate() {
        return expires;
    } 

    boolean hasExpired(Date date) {
        if (expires == null) {
            return true;
        } else {
            return date.before(expires);
        }
    }

    ...
}

Answer 3

+1 to the Long.MAX_VALUE suggestions. It seems that this would help you if you sort stuff by your date field.

However, instead of constructing a date from some the large constant value where ever you need the date, use a globally visible singleton to hold a Date instance that represents your special value:

class DateUtil
{
  public static final Date NO_EXPIRE = new Date( Long.MAX_VALUE );
}

Then you can use simple identity comparison (mydate == DateUtils.NO_EXPIRE) to test if a particular date is of your special case instead of obj.equals(); (ie. mydate.equals ( DateUtils.NO_EXPIRE ); )

Answer 4

Here is what I do:

public static final TimeZone UTC;

// 0001.01.01 12:00:00 AM +0000
public static final Date BEGINNING_OF_TIME;

// new Date(Long.MAX_VALUE) in UTC time zone
public static final Date END_OF_TIME;

static
{
    UTC = TimeZone.getTimeZone("UTC");
    final Calendar c = new GregorianCalendar(UTC);
    c.set(1, 0, 1, 0, 0, 0);
    c.set(Calendar.MILLISECOND, 0);
    BEGINNING_OF_TIME = c.getTime();
    c.setTime(new Date(Long.MAX_VALUE));
    END_OF_TIME = c.getTime();
}

Note that if the TimeZone is NOT UTC you will get offsets from the "end of time", which won't be maximal values. These are especially useful for inserting into Database fields and not having to have NULL dates.

Answer 5

have you considered adopting the use of Joda Time ?

It's slated to be included in java 7 as the basis for JSR-310

The feature that may interest you is ZeroIsMaxDateTimeField which basically swaps zero fields for the maximum value for that field within the date-time.

Answer 6

从 Java SE 8 开始，您可以使用：

LocalDate.MAX

Answer 7

One problem I see is that for sorting on expiration date, using a null isn't easily sortable. So replacing with an actual value (even if it's an arbitrary sentry value well into the future) may be needed.

I suppose another way of treating "no expiration" is simply to say something expires 100 years in the future... Unless your database is dealing with long-term contracts!

Answer 8

I like Instant.MAX because it is more likely to be supported in the future than Long.MAX_VALUE.

Note that as of today, though, Instant.MAX.toEpochMilli() throws an overflow error.

Answer 9

Perhaps one option is to use the maximal system date. You can get it by using:

System.out.println(new Date(Long.MAX_VALUE).toString())
//Output:
//Sun Aug 17 12:42:55 IST 292278994