Compare Date objects with different levels of precision

Question

I have a JUnit test that fails because the milliseconds are different. In this case I don\'t care about the milliseconds. How can I change the precision of the assert to i

Answer 1

You could do something like this:

assertTrue((date1.getTime()/1000) == (date2.getTime()/1000));

No String comparisons needed.

Answer 2

If you were using Joda you could use Fest Joda Time.

Answer 3

Just compare the date parts you're interested in comparing:

Date dateOne = new Date();
dateOne.setTime(61202516585000L);
Date dateTwo = new Date();
dateTwo.setTime(61202516585123L);

assertEquals(dateOne.getMonth(), dateTwo.getMonth());
assertEquals(dateOne.getDate(), dateTwo.getDate());
assertEquals(dateOne.getYear(), dateTwo.getYear());

// alternative to testing with deprecated methods in Date class
Calendar calOne = Calendar.getInstance();
Calendar calTwo = Calendar.getInstance();
calOne.setTime(dateOne);
calTwo.setTime(dateTwo);

assertEquals(calOne.get(Calendar.MONTH), calTwo.get(Calendar.MONTH));
assertEquals(calOne.get(Calendar.DATE), calTwo.get(Calendar.DATE));
assertEquals(calOne.get(Calendar.YEAR), calTwo.get(Calendar.YEAR));

Answer 4

This is actually a harder problem than it appears because of the boundary cases where the variance that you don't care about crosses a threshold for a value you are checking. e.g. the millisecond difference is less than a second but the two timestamps cross the second threshold, or the minute threshold, or the hour threshold. This makes any DateFormat approach inherently error-prone.

Instead, I would suggest comparing the actual millisecond timestamps and provide a variance delta indicating what you consider an acceptable difference between the two date objects. An overly verbose example follows:

public static void assertDateSimilar(Date expected, Date actual, long allowableVariance)
{
    long variance = Math.abs(allowableVariance);

    long millis = expected.getTime();
    long lowerBound = millis - allowableVariance;
    long upperBound = millis + allowableVariance;

    DateFormat df = DateFormat.getDateTimeInstance();

    boolean within = lowerBound <= actual.getTime() && actual.getTime() <= upperBound;
    assertTrue(MessageFormat.format("Expected {0} with variance of {1} but received {2}", df.format(expected), allowableVariance, df.format(actual)), within);
}

Answer 5

You can chose which precision level you want when comparing dates, e.g.:

LocalDateTime now = LocalDateTime.now().truncatedTo(ChronoUnit.SECONDS);
// e.g. in MySQL db "timestamp" is without fractional seconds precision (just up to seconds precision)
assertEquals(myTimestamp, now);

Answer 6

i cast the objects to java.util.Date and compare

assertEquals((Date)timestamp1,(Date)timestamp2);