CODEWITHSUNDEEP
javadate-formatgregorian-calendar
JMV12
JMV12

Reputation: 1035

GregorianCalendar and DateFormat Java

I am trying to do a simple exercise where I take a date, add 90 days to it, and format it to something like this:

Monday, April 20, 1998.

I am to do this using GregorianCalendar and DateFormat. So far, I have this compiling code, but I get a runtime error where I cannot format the given Object as Date:

import java.util.*;
import java.text.*;

class Assignment21 {
    public static void main(String args[]) {
        GregorianCalendar ddate = new GregorianCalendar(1994, 10, 20);
        ddate.add(Calendar.DAY_OF_MONTH, 90);
        SimpleDateFormat sdf = new SimpleDateFormat("EEE, MM dd, yyyy");
        String date = sdf.format(ddate);
    }
}

How can I correctly output the predefined GregorianCalendar date using DateFormat?

Upvotes: 0

Views: 2475

Answers (2)

Basil Bourque
Basil Bourque

Reputation: 338211

tl;dr

LocalDate.of( 1994 , Month.OCTOBER , 20 )                  // Generate a date-only value, a `LocalDate` object, without time-of-day and without time zone.
.plusDays( 90 )                                            // Add a span of time. Using immutable objects, a new `LocalDate` object is instantiated, without altering the first.
.format(                                                   
    DateTimeFormatter.ofLocalizedDate( FormatStyle.FULL )
                     .withLocale( Locale.US )
)

Wednesday, January 18, 1995

java.time

You are using troublesome old date-time classes that are now legacy, supplanted by the java.time classes. 

LocalDate ld = LocalDate.of( 1994 , 10 , 20 ) ; // Sane numbering for year and month, unlike legacy classes. '1994' = 1994, and 10 = October.
LocalDate ldLater = ld.plusDays( 90 ) ;

Or use Month enum.

LocalDate ld = LocalDate.of( 1994 , Month.OCTOBER , 20 ) ; 
LocalDate ldLater = ld.plusDays( 90 ) ;

Let java.time automatically localize for you. 

DateTimeFormatter f = DateTimeFormatter.ofLocalizedDate( FormatStyle.FULL ).withLocale( Locale.US ) ;
String output = ldLater.format( f ) ;

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?

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.

Upvotes: 2

assembler
assembler

Reputation: 3302

You have to correct your code:

instead of 

String date = sdf.format(ddate);

try:

String date = sdf.format(ddate.getTime());

Upvotes: 2

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