ChronoLocalDateTime compareTo() method in Java with Examples

The compareTo() method is used to compare two ChronoLocalDateTime objects for order. It returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

Syntax:

public int compareTo(ChronoLocalDateTime<?> other)

Parameters: - other: the other ChronoLocalDateTime to compare to, not null.

Returns: - a negative integer if this ChronoLocalDateTime is less than other. - zero if this ChronoLocalDateTime is equal to other. - a positive integer if this ChronoLocalDateTime is greater than other.

Examples:

• Comparing two ChronoLocalDateTime objects using compareTo() method:

import java.time.LocalDateTime;
import java.time.chrono.ChronoLocalDateTime;

public class Example {
    public static void main(String[] args) {
        LocalDateTime dateTime1 = LocalDateTime.of(2021, 10, 1, 10, 30);
        LocalDateTime dateTime2 = LocalDateTime.of(2021, 10, 1, 11, 30);

        ChronoLocalDateTime<?> chronoDateTime1 = dateTime1;
        ChronoLocalDateTime<?> chronoDateTime2 = dateTime2;

        int result = chronoDateTime1.compareTo(chronoDateTime2);

        if (result < 0) {
            System.out.println(dateTime1 + " is before " + dateTime2);
        } else if (result == 0) {
            System.out.println(dateTime1 + " is equal to " + dateTime2);
        } else {
            System.out.println(dateTime1 + " is after " + dateTime2);
        }
    }
}

Output:

2021-10-01T10:30 is before 2021-10-01T11:30

• Comparing two ChronoLocalDateTime objects of different chronologies using compareTo() method:

import java.time.LocalDateTime;
import java.time.chrono.HijrahDate;
import java.time.chrono.IsoChronology;
import java.time.chrono.ChronoLocalDateTime;

public class Example {
    public static void main(String[] args) {
        LocalDateTime dateTime = LocalDateTime.of(2021, 10, 1, 10, 30);
        HijrahDate hijrahDate = HijrahDate.from(dateTime);

        ChronoLocalDateTime<?> chronoDateTime1 = dateTime;
        ChronoLocalDateTime<?> chronoDateTime2 = hijrahDate.atTime(10, 30);

        int result = chronoDateTime1.compareTo(chronoDateTime2);

        if (result < 0) {
            System.out.println(dateTime + " is before " + hijrahDate);
        } else if (result == 0) {
            System.out.println(dateTime + " is equal to " + hijrahDate);
        } else {
            System.out.println(dateTime + " is after " + hijrahDate);
        }
    }
}

Output:

2021-10-01T10:30 is after AH 1443-02-22T10:30 (Hijrah calendar)