Question

I have some data about opening hours I’m trying to represent using Joda-Time.

The typical opening hours of day look like this:

Open from 9 to 12, and from 13 to 20.

My main reason for representing them in Joda-Time entities, is to validate them:

• Check that opening hours are valid (9 is before 12, etc)
• Check that no open-intervals overlap (“9-12 and 11-13” are illegal)

API-wise, the Joda-Time Interval class has the methods I need for doing this validation, but Intervals are pairs of instants in the date-time-continuum. I would like to represent them independent of absolute time, kind of like an Interval of two LocalTime partials. Is this possible?

Answer 1

Here’s an attempt at a custom TimeInterval (pretty much like the solution Gray commented):

import org.joda.time.*;

public class TimeInterval {
    private static final Instant CONSTANT = new Instant(0);
    private final LocalTime from;
    private final LocalTime to;

    public TimeInterval(LocalTime from, LocalTime to) {
        this.from = from;
        this.to = to;
    }

    public boolean isValid() {
        try { return toInterval() != null; } 
        catch (IllegalArgumentException e) { return false;}
    }

    public boolean overlapsWith(TimeInterval timeInterval) {
        return this.toInterval().overlaps(timeInterval.toInterval());
    }

    /**
     * @return this represented as a proper Interval
     * @throws IllegalArgumentException if invalid (to is before from)
     */
    private Interval toInterval() throws IllegalArgumentException {
        return new Interval(from.toDateTime(CONSTANT), to.toDateTime(CONSTANT));
    }
}