Compare multiple set of date periods

Question

I have 3 sets of start date and end dates
1st - start date (01/25/2017) and an end date (02/26/2017)
2nd - set of (01/25/2017) and an end date (02/26/2017)
3rd - set (03/25/2017) and an end date (04/26/2017)

I want to write a Java program to compare the 3 sets and give me the two sets which are equal:

((01/25/2017) - (02/26/2017))

Note that start date and end date comes from two different variables.

Answer 1

org.threeten.extra.LocalDateRange::equals

See the ThreeTen-Extra project for the LocalDateRange class with its equals method. This method compares one LocalDateRange with another ensuring that the pair of dates are the same.

That class depends on the java.time.LocalDate class built into Java 8 and later. That class has been covered many hundreds of times on this site. So search Stack Overflow for further info.

LocalDateRange.of(
    LocalDate.of( 2017 , Month.JANUARY , 25 ) ,
    LocalDate.of( 2017 , Month.FEBRUARY , 26 )      // Returns a `LocalDate` object.
)                                                   // Returns a `LocalDateRange` object.
.equals(
    LocalDateRange.of(
        LocalDate.of( 2017 , Month.MARCH , 25 ) ,
        LocalDate.of( 2017 , Month.APRIL , 26 ) 
    )
)

false

ChronoUnit.DAYS::between

If you meant to compare the number of days elapsed, use ChronoUnit enum.

ChronoUnit.DAYS.between(
    LocalDate.of( 2017 , Month.JANUARY , 25 ) ,
    LocalDate.of( 2017 , Month.FEBRUARY , 26 ) 
)                                                   // Returns a `long` integer primitive.
 == 
ChronoUnit.DAYS.between(
    LocalDate.of( 2017 , Month.MARCH , 25 ) ,
    LocalDate.of( 2017 , Month.APRIL , 26 ) 
)

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Answer 2

One way to do this is to create a custom class (MyDateSets) which holds a set of start and end dates. The class's equals method (override the Object's equals) specifies the date set equality.

The example code:

import java.time.*;
import java.time.format.*;
public class CompareDateSets {
    public static void main(String [] args) {
        // Parse date strings to LocalDate objects
        // Make 3 set sof them - the input
        DateTimeFormatter parser = DateTimeFormatter.ofPattern("MM/dd/yyyy");
        LocalDate start1 = LocalDate.parse("01/25/2017", parser);
        LocalDate end1 = LocalDate.parse("01/25/2017", parser);
        LocalDate start2 = LocalDate.parse("01/25/2017", parser);
        LocalDate end2 = LocalDate.parse("01/25/2017", parser);
        LocalDate start3 = LocalDate.parse("03/25/2017", parser);
        LocalDate end3 = LocalDate.parse("04/26/2017", parser);
        // Create MyDateSets objects - 3 sets of input
        MyDateSets set1 = new MyDateSets(start1, end1);
        MyDateSets set2 = new MyDateSets(start2, end2);
        MyDateSets set3 = new MyDateSets(start3, end3);
        // Compare each set and print the comparison result
        System.out.println(set1.equals(set2)); // true
        System.out.println(set1.equals(set3));  // false
        System.out.println(set2.equals(set3));  // false
    }
}

/*
 * Custom class has a set of the start and end dates.
 * Overrides Object class's equals method to define
 * the date set's equality.
 */
class MyDateSets {
    private LocalDate start;
    private LocalDate end;
    public MyDateSets(LocalDate start, LocalDate end) {
        this.start = start;
        this.end = end;
    }
    public LocalDate getStart() {
        return start;
    }
    public LocalDate getEnd() {
        return end;
    }
    @Override
    public boolean equals(Object o) {
        MyDateSets dates = (MyDateSets) o;
        if ((dates.getStart().equals(start)) &&
                (dates.getEnd().equals(end))) {
            return true;
        }
        return false;
    }
}