Make a union of two Joda-Time Interval objects

Question

In Joda-Time , is there any way to create a Interval as a union of two other intervals. I know there is intersection method which is called overlap (and overlaps ). But I can not see any union methods.

Answer 1

If you want an interval that "covers" two others, just create a new interval that runs from min(a.start, b.start) to max(a.end, b.end) .

If you need to represent the gap as well, then you'll need to write your own classes to handle the behavior you want. There's nothing builtin to Joda-time for this as there are several possible interpretations of what it means to "union" non-contiguous intervals.

Answer 2

The answer by Jim Garrison is correct, but brief. I decided to try an implementation. Using Joda-Time 2.3 with Java 7 on a Mac.

If you made much use of this kind of "union" method, perhaps you should consider creating a subclass of Interval to add a method where you pass a single (second) Interval to be compared to the first, the one whose method is being called.

For occasional use, a static method stuck away on some utility class would suffice. That's what I wrote here, a static method where you pass a pair of Intervals. A new Interval is returned.

Rather than use multiple-line if statements, my example code uses the ?: ternary operator to collapse to one line the decision to pull the first or second DateTime .

Static method…

// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.

static Interval union( Interval firstInterval, Interval secondInterval ) 
{
    // Purpose: Produce a new Interval instance from the outer limits of any pair of Intervals.

    // Take the earliest of both starting date-times.
    DateTime start =  firstInterval.getStart().isBefore( secondInterval.getStart() )  ? firstInterval.getStart() : secondInterval.getStart();
    // Take the latest of both ending date-times.
    DateTime end =  firstInterval.getEnd().isAfter( secondInterval.getEnd() )  ? firstInterval.getEnd() : secondInterval.getEnd();
    // Instantiate a new Interval from the pair of DateTime instances.
    Interval unionInterval = new Interval( start, end );

    return unionInterval;
}

Example usage…

// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
// import org.joda.time.*;
// import org.joda.time.format.*;

// Note the various time zones.
Interval i1 = new Interval( new DateTime( 2013, 1, 1, 0, 0, 0, DateTimeZone.forID( "America/Montreal" ) ), new DateTime( 2013, 1, 5, 0, 0, 0, DateTimeZone.forID( "America/Montreal" ) ) );
Interval i2 = new Interval( new DateTime( 2013, 1, 10, 0, 0, 0, DateTimeZone.forID( "Europe/Paris" ) ), new DateTime( 2013, 1, 15, 0, 0, 0, DateTimeZone.forID( "Europe/Paris" ) ) );

Interval i3 = TimeExample.union( i1, i2 );

Dump to console…

System.out.println("i1: " + i1 );
System.out.println("i2: " + i2 );
// Note that Joda-Time adjusts the ending DateTime's time zone to match the starting one.
System.out.println("i3: " + i3 );

When run…

i1: 2013-01-01T00:00:00.000-05:00/2013-01-04T18:00:00.000-05:00
i2: 2013-01-10T00:00:00.000+01:00/2013-01-15T00:00:00.000+01:00
i3: 2013-01-01T00:00:00.000-05:00/2013-01-14T18:00:00.000-05:00