Example in this link is not working

[Saran Vinaiyak]

Link: https://www.ical4j.org/examples/model/#creating-a-meeting-of-four-hour-duration

I have corrected the compilation errors in the above example and yet when I run it. This is my output. Please help.

BEGIN:VCALENDAR
END:VCALENDAR

I am getting this error when I call Calendar#validate :

net.fortuna.ical4j.validate.ValidationException: Content [PRODID] must be specified once
    at net.fortuna.ical4j.validate.Validator.assertFalse(Validator.java:53)

Here is my code:

import net.fortuna.ical4j.data.CalendarOutputter
import net.fortuna.ical4j.model.DateTime
import net.fortuna.ical4j.model.TimeZoneRegistry
import net.fortuna.ical4j.model.TimeZoneRegistryFactory
import net.fortuna.ical4j.model.component.VEvent
import net.fortuna.ical4j.model.component.VTimeZone
import net.fortuna.ical4j.model.parameter.Cn
import net.fortuna.ical4j.model.parameter.Role
import net.fortuna.ical4j.model.property.Attendee
import net.fortuna.ical4j.model.property.CalScale
import net.fortuna.ical4j.model.property.ProdId
import net.fortuna.ical4j.model.property.Uid
import net.fortuna.ical4j.model.property.Version
import net.fortuna.ical4j.util.Calendars
import net.fortuna.ical4j.util.MapTimeZoneCache
import net.fortuna.ical4j.util.RandomUidGenerator
import net.fortuna.ical4j.util.UidGenerator

import java.time.LocalDateTime
import java.time.Month
import java.time.ZoneId

System.setProperty("net.fortuna.ical4j.timezone.cache.impl", MapTimeZoneCache.class.getName());
// Create a TimeZone
TimeZoneRegistry registry = TimeZoneRegistryFactory.getInstance().createRegistry();
TimeZone timezone = registry.getTimeZone("America/Mexico_City");
VTimeZone tz = timezone.getVTimeZone();

// Start Date is on: April 1, 2008, 9:00 am
java.util.Calendar startDate = new GregorianCalendar();
startDate.setTimeZone(timezone);
startDate.set(java.util.Calendar.MONTH, java.util.Calendar.APRIL);
startDate.set(java.util.Calendar.DAY_OF_MONTH, 1);
startDate.set(java.util.Calendar.YEAR, 2008);
startDate.set(java.util.Calendar.HOUR_OF_DAY, 9);
startDate.set(java.util.Calendar.MINUTE, 0);
startDate.set(java.util.Calendar.SECOND, 0);

// End Date is on: April 1, 2008, 13:00
java.util.Calendar endDate = new GregorianCalendar();
endDate.setTimeZone(timezone);
endDate.set(java.util.Calendar.MONTH, java.util.Calendar.APRIL);
endDate.set(java.util.Calendar.DAY_OF_MONTH, 1);
endDate.set(java.util.Calendar.YEAR, 2008);
endDate.set(java.util.Calendar.HOUR_OF_DAY, 13);
endDate.set(java.util.Calendar.MINUTE, 0);
endDate.set(java.util.Calendar.SECOND, 0);

// Create the event
String eventName = "Progress Meeting";
LocalDateTime start = LocalDateTime.of(2023, Month.APRIL, 30, 12, 00)
LocalDateTime end = LocalDateTime.of(2023, Month.APRIL, 30, 12, 30)
VEvent meeting = new VEvent(start, end, eventName);

// add timezone info..
meeting.getProperties().add(tz.getTimeZoneId().get());

// generate unique identifier..
UidGenerator ug = new RandomUidGenerator();
Uid uid = ug.generateUid();
meeting.getProperties().add(uid);

// add attendees..
Attendee dev1 = new Attendee(URI.create("mailto:dev1@mycompany.com"));
dev1.getParameters().add(Role.REQ_PARTICIPANT);
dev1.getParameters().add(new Cn("Developer 1"));
meeting.getProperties().add(dev1);

Attendee dev2 = new Attendee(URI.create("mailto:dev2@mycompany.com"));
dev2.getParameters().add(Role.OPT_PARTICIPANT);
dev2.getParameters().add(new Cn("Developer 2"));
meeting.getProperties().add(dev2);

// Create a calendar
net.fortuna.ical4j.model.Calendar icsCalendar = new net.fortuna.ical4j.model.Calendar();
icsCalendar.getProperties().add(Version.VERSION_2_0);
icsCalendar.getProperties().add(new ProdId("-//Events Calendar//iCal4j 1.0//EN"));

icsCalendar.getProperties().add(CalScale.GREGORIAN);



// Add the event and print
icsCalendar.getComponents().add(meeting);
System.out.println(icsCalendar.validate());

OutputStream byteOutputStream = new ByteArrayOutputStream();
CalendarOutputter calendarOutputter = new CalendarOutputter(false)
calendarOutputter.output(icsCalendar, byteOutputStream)

println new String(byteOutputStream.toByteArray())

[Saran Vinaiyak]

I figured it out. I was using 4.0.0-alpha version. However, when I switched it to the version: 3.2.2 it worked fine.