Comparing instances of java.time.ZonedDateTime ignoring seconds and milliseconds instants from comparisons in Java 8

Question

I am looking for an equivalent way of Joda Time in Java 8 comparing instances of org.joda.time.DateTime (with a time zone specified) ignoring seconds and milliseconds from comparisons as follows.

DateTimeFormatter formatter = DateTimeFormat.forPattern("dd-MMM-yyyy hh:mm:ss:SSS a Z").withZone(DateTimeZone.forID("Asia/Kolkata"));
DateTime first = formatter.parseDateTime("16-Feb-2012 12:03:45:999 AM +05:30");
DateTime second = formatter.parseDateTime("16-Feb-2012 12:03:55:999 AM +05:30");

DateTimeComparator comparator = DateTimeComparator.getInstance(DateTimeFieldType.minuteOfHour());
int compare = comparator.compare(first, second);
System.out.println("compare : " + compare);

The comparison returns 0 meaning that both the objects have been considered equal after ignoring seconds and milliseconds instants from the comparison.

Fields of a magnitude less than the lower limit specified with DateTimeFieldType are ignored here.

What is the equivalent way of doing the same thing using the Java Time API in Java 8?

_{To be honest, I did not succeed to achieve the same in Java 8 with my attempts.}

Answer 1

As Java-8 introduced lambdas and method references, having dedicated Comparator classes became mostly unnecessary, so they are absent in java.time. You may write instead:

Comparator<ZonedDateTime> comparator = Comparator.comparing(
      zdt -> zdt.truncatedTo(ChronoUnit.MINUTES));

Complete example:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MMM-yyyy hh:mm:ss:SSS a X")
        .withLocale(Locale.ENGLISH).withZone(ZoneId.of("Asia/Kolkata"));
ZonedDateTime first = ZonedDateTime.parse("16-Feb-2012 12:03:45:999 AM +0530", formatter);
ZonedDateTime second = ZonedDateTime.parse("16-Feb-2012 12:03:55:999 AM +0530", formatter);
Comparator<ZonedDateTime> comparator = Comparator.comparing(
        zdt -> zdt.truncatedTo(ChronoUnit.MINUTES));
System.out.println(comparator.compare(first, second));