How to compare dates in Java?

Including the dates in range

Often, you want to see if a date falls within a specific range, and the border dates should count:

LocalDate startDate = LocalDate.parse("2023-01-01");
LocalDate endDate = LocalDate.parse("2023-12-31");

// Is 'today' between 'startDate' (inclusive) and 'endDate' (inclusive)?
boolean isWithinRange = !today.isBefore(startDate) && !today.isAfter(endDate);
System.out.println(isWithinRange); // Output depends on today's shenanigans
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This tells us if today is in the inclusive range of the start and end dates.

Time travel across time zones

Time zones can turn simple date comparisons into a world tour. Here's ZonedDateTime taking us from now to UTC:

ZonedDateTime zonedNow = ZonedDateTime.now();
ZonedDateTime zonedTomorrow = zonedNow.plusDays(1).withZoneSameInstant(ZoneId.of("UTC"));

System.out.println(zonedNow.isBefore(zonedTomorrow)); // true (unless you live in UTC)
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With this, you can compare dates accurately across different time zones.

Beware! Here be dragons (Edge cases)

Dates are sprinkled with interesting edge cases. Here's your sword and shield:

Leap years and daylight savings

When dealing with leap years or daylight savings, avoid the dragon's fire with ZonedDateTime.

Null dates - the invisible dragon

Demolish the invisible foe, NullPointerException, by always checking for null:

LocalDate otherDate = // ...
if (otherDate != null && today.isAfter(otherDate)) {
    // The 'null' dragon is not here, safe to proceed.
}
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Legacy Date and Calendar - ancient dragons

If you're stuck with the ancient dragons Date or Calendar, here's your map:

Date date1 = new Date();
Calendar calendar = Calendar.getInstance();
calendar.setTime(date1);
calendar.add(Calendar.DATE, 1);
Date date2 = calendar.getTime();

System.out.println(date2.after(date1)); // true (if your map is in the right orientation)
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But try upgrading your gear to java.time if you can.

Database dates - the hidden dungeons

Working with database dates? Equip your java.time objects using JDBC 4.2 or later to limit conversions and overhead:

PreparedStatement pstmt = con.prepareStatement("SELECT * FROM mytable WHERE date_column = ?");
pstmt.setObject(1, LocalDate.now());
ResultSet rs = pstmt.executeQuery();
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With this, you're using modern equipment in database dungeons.