want compare Java.time.LocalDate & java.time.LocalTime in compareTo()

Question

I have a Meeting class that implements Comparable<Meeting>. Overridden compareTo method will compare meetingDate of two Meeting objects first and in case they are equal it will compare their meetingTime. I want to put all my Meeting objects in a ProirtiyQueue<Meeting> so I can retrieve the upcoming meetings as per their meetingDate and meetingTime. Data type used are java.time.LocalDate and java.time.LocalTime respectively. How can I compare meetingDate and meetingTime in my compareTo(Meeting o) method.

 public class Meeting implements Comparable<Meeting> {

private String title;
private String desciption;
private LocalDate meetingDate;
private LocalTime meetingTime;

public Meeting(String title, String description, LocalDate meetingDate, LocalTime meetingTime) {
    this.title = title;
    this.desciption = description;
    this.meetingDate = meetingDate;
    this.meetingTime = meetingTime;

}

public String getTittle() {
    return title;
}

public void setTittle(String title) {
    this.title = title;
}

public String getDescription() {
    return desciption;
}

public void setDescription(String description) {
    this.desciption = description;
}

public LocalDate getMeetingDate() {
    return meetingDate;
}
public void setMeetingDate(LocalDate meetingDate) {
    this.meetingDate = meetingDate;
}

public LocalTime getMeetingTime() {
    return meetingTime;
}

public void setMeetingTime(LocalTime meetingTime) {
    this.meetingTime = meetingTime;
}

public int compareTo(Meeting o) {
    // comparison
}


}

Answer 1

You can delegate the implementation of compareTo to a Comparator which can chain comparisons of multiple properties of the given Meeting:

public class Meeting {
    ...

    private static final Comparator<Meeting> comparator =
        Comparator.comparing(Meeting::getMeetingDate)
            .thenComparing(Meeting::getMeetingTime);

    @Override
    public int compareTo(Meeting that) {
        comparator.compare(this, that);
    }

Answer 2

As per the documentation,

Date.compareTo()

Return : an int < 0 if this Date is less than the specified Date, 0 if they are equal, and an int > 0 if this Date is greater.

Time.before()

true if this time is less than the given time

Then you need something like :

public int compareTo(Meeting o) {
    if (o == null)
      return (0);
    if (o.meetingDate.compareTo(meetingDate) == 0)
      return (o.meetingTime.before(meetingTime));
    else
      return (o.meetingDate.compareTo(meetingDate));
}

This function will return : "An int < 0" if o is before the currentMeeting object. "An int > 0" if o is after the currentMeeting object.