GregorianCalendar from(ZonedDateTime) in Java

from(ZonedDateTime): This method is available in java.util.GregorianCalendar class of Java.

Syntax:

GregorianCalendar java.util.GregorianCalendar.from(ZonedDateTime zdt)

This method takes one argument. This method obtains an instance of GregorianCalendar with the default locale from a ZonedDateTime object.

Parameters: One parameter is required for this method.

zdt: the zoned date-time object to convert.

Returns: the gregorian calendar representing the same point on the timeline as the zoned date-time provided.

Throws:

1. NullPointerException - if zdt is null.

2. IllegalArgumentException - if the zoned date-time is too large to represent as a GregorianCalendar.

Approach 1: When no exception

Java

import java.time.ZonedDateTime;
import java.util.GregorianCalendar;

public class GregorianCalendarfrom {
    public static void main(String[] args) {

        ZonedDateTime zdt = ZonedDateTime.now();
        System.out.println(GregorianCalendar.from(zdt));

    }
}

Output:

java.util.GregorianCalendar[time=1644077834745,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="Asia/Calcutta",offset=19800000,dstSavings=0,useDaylight=false,transitions=7,lastRule=null],firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2022,MONTH=1,WEEK_OF_YEAR=5,WEEK_OF_MONTH=1,DAY_OF_MONTH=5,DAY_OF_YEAR=36,DAY_OF_WEEK=7,DAY_OF_WEEK_IN_MONTH=1,AM_PM=1,HOUR=9,HOUR_OF_DAY=21,MINUTE=47,SECOND=14,MILLISECOND=745,ZONE_OFFSET=19800000,DST_OFFSET=0]

Approach 2: NullPointerException 

Java

import java.time.ZonedDateTime;
import java.util.GregorianCalendar;

public class GregorianCalendarfrom {
    public static void main(String[] args) {

        ZonedDateTime zdt = null;
        System.out.println(GregorianCalendar.from(zdt));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.time.ZonedDateTime.getZone()" because "zdt" is null
	at java.base/java.util.GregorianCalendar.from(GregorianCalendar.java:3287)