How to compare two dates without the use of objects?

Question

/** Reports whether or not date1 comes earlier in time than date2. For example, isEarlierThan("12-01-2015", "02-15-2017") is true but isEarlierThan("10-11-2016", "10-11-2016") and isEarlierThan("09-09-1967", "02-15-1933")is false. * /

public static boolean isEarlierThan (String date1, String date2) 

{
    if(date1.compareTo(date2) > 0) {
        return true;
    }
    else if (date1.compareTo(date2) <= 0) {
        return false;
    }
    else {
        return true;
    }
}

This code works sometimes but no always. I have ran a tests case and it fails. The following test case is below.

public void testIsEarlierThan () 
{
    assertTrue(isEarlierThan("12-01-2015", "02-15-2017"));
    assertFalse(isEarlierThan("10-11-2016", "10-11-2016"));
    assertFalse(isEarlierThan("09-09-1967", "02-15-1933"));
    assertTrue(isEarlierThan("02-14-2017", "02-15-2017"));
}

When I run the test case, only the first two work then it stops at the third one. But I don't understand whats wrong? if the first one works shouldn't the third one work just fine? Thanks in advance!

because this is how string comparison works, `9` is after `2` for 3rd example — Iłya Bursov, Sep 07 '17 at 02:27
Why? when `Date.compareTo()` already works? and this doesn't? Can't? What is your aversion to using objects? — user207421, Sep 07 '17 at 02:27
Of course, but that gives the wrong answer, because 2015 is before 2017. — user207421, Sep 07 '17 at 02:29
@EJP my aversion to it is that my teacher won't let us. He insists that we find another to do it but I don't know another way except string comparison which also doesn't work. — SassyRegards201, Sep 07 '17 at 02:29
You have to isolate the year, the month, and the day, and compare them in that order. — user207421, Sep 07 '17 at 02:30
Ok. that helps. so basically substring then compare then concat? — SassyRegards201, Sep 07 '17 at 02:31

SassyRegards201 · Accepted Answer · 2017-09-08T00:39:27.463

Answering my own question. And for future reference if anyone has a similar question.

public static boolean isEarlierThan (String date1, String date2)
{

    String month1 = date1.substring(0, 2);
    String month2 = date2.substring(0, 2);

    String day1 = date1.substring(3, 5);
    String day2 = date2.substring(3, 5);

    String year1 = date1.substring(6, 10);
    String year2 = date2.substring(6, 10);

    date1 = year1 + month1 + day1; // + month1 + day1
    date2 = year2 + month2 + day2; // + month2 + day2

    if (date1.compareTo(date2) < 0)
    {
        return true;
    }
    else if (date1.compareTo(date2) > 0)
    {
        return false;
    }
    else
    {
        return false;
    }
}

Basically I have a method that takes the two dates, takes them apart into a year, a month, and a day. Then puts them back together in a different order so that when I compare them it will print the which true if date1 is before date2 or false if date1 is after or equal to date2.

How to compare two dates without the use of objects?

1 Answers1