CODEWITHSUNDEEP
javaandroiddatecalendar
Positive-One
Positive-One

Reputation: 99

Java/Android: Literally Compare date of 2 Calendar objects

I am trying to compare 2 calendar objects with their dates.

My code: 

Calendar c1 = Calendar.getInstance(); 
Calendar c2 = Calendar.getInstance(); 

c1.set(2017, 1,2); 
c2.set(2017, 1,1); 

int compared = c1.compareTo(c2);

textView.setText("" + compared);

The result should be an int of either -1 or 1, in which my case should be: -1.

However, this is not the result I want. I want to be able to compare dates directly say: 

01/20/2010 compared to 02/30/2014 returns true or false.

Is there some ways to achieve this based on the Calendar lib?

I am aware of built in methods such as getDay(), getMonth(), equals() and so on. The problem is that in using getDay(), getMonth(), getYear(), it is very difficult to make a comparison as I'm comparing between 3 ints.

Also, I got a feeling that to compare between 2 dates, I will have to set the timezone and the timeinMillis to be the same. Meaning to compare the date direct, for cal1 and cal2, its time zone and timeinmillis has to be the same.

Can someone clarify this to me?

Upvotes: 0

Views: 1243

Answers (4)

Basil Bourque
Basil Bourque

Reputation: 340118

tl;dr

LocalDate.of( 2010 , 1 , 20 )
         .isBefore( 
             LocalDate.of( 2014 , 2 , 30 ) 
         )

true

Details

You are using the wrong method on the wrong class.

The Calendar class represents a date and time-of-day. But you want a date-only value without a time-of-day.

You are calling the compareTo method which is defined by a specific interface Comparable with a specific purpose. This method is designed to return integers whereas you want a boolean result of "isBefore" or "isAfter".

Using java.time

Also, the troublesome Calendar class is one of the old date-time classes that are now legacy, supplanted by the java.time classes.

The LocalDate class represents a date-only value without time-of-day and without time zone.

LocalDate ld1 = LocalDate.of( 2010 , 1 , 20 ) ;
LocalDate ld2 = LocalDate.of( 2014 , 2 , 30 ) ;

Compare with boolean methods.

boolean ld1IsBefore = ld1.isBefore( ld2 );
boolean ld1IsAfter = ld1.isAfter( ld2 );
boolean ld1IsEqual = ld1.isEqual( ld2 );

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.

Where to obtain the java.time classes?

Upvotes: 1

GhostCat
GhostCat

Reputation: 140613

You should be careful there from a conceptual point of view: compareTo() has that very specific meaning of returning an int, with that - 1, 0,1 results telling you about how to order the compared objects.

That boolean result you are looking for indicates that you should think/speak using verbs like equals, before, or after!

It is a bad idea to take a well defined concept, keeping the name but changing the meaning under the covers!

Upvotes: 2

Scary Wombat
Scary Wombat

Reputation: 44854

you can do it this way

textView.setText("c1 compared to c2 returns " + (c1.compareTo(c2) == 0));

As per the javadocs

Compares the time values (millisecond offsets from the Epoch) represented by two Calendar objects.

Test

        Calendar c1 = Calendar.getInstance();
        Calendar c2 = Calendar.getInstance();
        c2.add(Calendar.MINUTE, 1);

        System.out.println ("c1 compared to c2 returns " + (c1.compareTo(c2) == 0));

Upvotes: 0

Ousmane D.
Ousmane D.

Reputation: 56469

you could use either Calendar#before or Calendar#after to make a comparison which returns a boolean.

SimpleDateFormat formatC1 = new SimpleDateFormat("yyyy-MM-dd");
String formattedC1 = formatC1.format(c1.getTime());
SimpleDateFormat formatC2 = new SimpleDateFormat("yyyy-MM-dd");
String formattedC2 = formatC2.format(c2.getTime());
textView.setText(formattedC1 + " compared to " + formattedC2 + " returns " + c1.before(c2));

Upvotes: 1

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