Java Calendar Class

Java Calendar Class with Examples

In this article, I am going to discuss Java Calendar Class with Examples. Please read our previous article where we discussed Date and Time API in Java.

Java Calendar Class:

java.util.Calendar is an abstract class. It provides methods for converting date between a specific instant in time and a set of calendar fields such as MONTH, YEAR, HOUR, etc. We cannot use a constructor to create an instance because it is an Abstract class. Therefore, we have to use the static method Calendar.getInstance() to instantiate and implement a sub-class.

Calendar.getInstance(): It returns a Calendar instance based on the current time in the default time zone with the default locale.
Calendar.getInstance(TimeZone zone)
Calendar.getInstance(Locale aLocale)
Calendar.getInstance(TimeZone zone, Locale aLocale)

The important points about Calendar

It also provides additional fields and methods for implementing a concrete calendar system outside the package. It defines the range of values returned by certain calendar fields.

Declaration: public abstract class Calendar extends Object implements Serializable, Cloneable, Comparable<Calendar>

Methods
  1. public void add(int field, int amount): It is used to add the specified amount of time to the given calendar field.
  2. public boolean after(Object when): It returns true if the time represented by this Calendar is after the time represented by when Object.
  3. public boolean before(Object when): It basically returns true if the time represented by this Calendar is before the time represented by when Object.
  4. public final void clear(int field): It is used to set the given calendar field value and the time value of this Calendar undefined.
  5. public Object clone(): It provides the copy of the current object.
  6. public int compareTo(Calendar anotherCalendar): It is used to compare the time value between two calendar objects.
  7. protected void complete(): It is used to fill any unset fields in the calendar fields.
  8. protected abstract void computeFields(): It is used to convert the current millisecond time value time to calendar field values in fields[].
  9. protected abstract void computeTime(): It is used to convert calendar field values in the field[] to the millisecond time value time.
  10. public boolean equals(Object object): It is used to compare two objects for equality and returns true if they are equal.
  11. public int get(int field): It is passed as the parameter and returns the value of fields passed as the parameter.
  12. public int getActualMaximum(int field): It returns the maximum possible value of the calendar field passed as the parameter to this method.
  13. public int getActualMinimum(int field): It returns the minimum possible value of the calendar field passed as the parameter to this method.
  14. public static Set<String> getAvailableCalendarTypes(): It returns a set which contains string set of all available calendar type supported by JRE.
  15. public static Locale[] getAvailableLocales(): It returns an array of all locales available in JRE.
  16. public String getCalendarType(): It returns all available calendar types supported by JRE.
  17. public String getDisplayName(int field, int style, Locale locale): It returns the String representation of the calendar field value passed as the parameter in a given style and local.
  18. public Map<String, Integer> getDisplayNames(int field, int style, Locale locale): It returns Map representation of the calendar field value passed as the parameter.
  19. public int getFirstDayOfWeek(): It returns the first day of the week in integer form.
  20. public abstract int getGreatestMinimum(int field): It returns the highest minimum value of the Calendar field passed as the parameter.
  21. public static Calendar getInstance(): It is used with calendar objects to get the instance of the calendar according to the current time zone set by JRE.
  22. public abstract int getLeastMaximum(int field): It returns the smallest value from all maximum value for the field specified as the parameter to the method.
  23. public abstract int getMaximum(int field): It is used with calendar object to get the maximum value of the specified calendar field as the parameter.
  24. public int getMinimalDaysInFirstWeek(): It returns required minimum days in integer form.
  25. public abstract int getMinimum(int field): It is used with calendar objects to get the minimum value of the specified calendar field as the parameter.
  26. public final Date getTime(): It gets the time value of the calendar object and returns the date.
  27. public long getTimeInMillis(): It returns the current time in millisecond. Its returns type is long.
  28. public TimeZone getTimeZone(): It gets the Time zone of calendar object and returns a Time zone object.
  29. public int getWeeksInWeekYear(): It returns total weeks in week year. It is returned in integer form.
  30. public int getWeekYear(): It gets the week year represented by current Calendar.
  31. public int hashCode(): It returns the hash code for calendar object.
  32. Protected final int internalGet(int field): It returns the value of the calendar field passed as the parameter.
  33. public boolean isLenient(): It returns the Boolean value True if the interpretation mode of this calendar is lenient; false otherwise.
  34. public final boolean isSet(int field): It will check if the specified field as the parameter has been set or not. Returns false if it is not set; otherwise true.
  35. public boolean isWeekDateSupported(): It will check if this calendar supports the week date. Its default value is false.
  36. public abstract void roll(int field, Boolean up): It increases or decreases the specified calendar field by one unit without affecting the other field.
  37. public void set(int field, int value): It sets the specified calendar field by the specified value.
  38. public void setFirstDayOfWeek(int value): It sets the first day of the week. The value to be set is passed as a parameter.
  39. public void setMinimalDaysInFirstWeek(int value): It sets the minimal days required in the first week. The value to be set is passed as a parameter.
  40. public final void setTime(Date date): It sets the time of the current calendar object.
  41. public void setTimeInMillis(long millis): It sets the current time in milliseconds.
  42. public void setTimeZone(TimeZone value): It sets the timeZone with passed TimeZone value as the parameter.
  43. public void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek): It sets the current date with specified integer value as the parameter.
  44. public final Instant toInstant(): It converts the current object to an instant.
  45. public String toString(): It returns the string representation of the current object.
Sample Program for Java Calendar Class
import java.util.Calendar;

public class CalendarDemo1
{
    public static void main (String[]args)
    {
        Calendar calendar = Calendar.getInstance ();
        System.out.println ("The current date is : " + calendar.getTime ());
        calendar.add (Calendar.DATE, -15);
        System.out.println ("15 days ago: " + calendar.getTime ());
        calendar.add (Calendar.MONTH, 4);
        System.out.println ("4 months later: " + calendar.getTime ());
        calendar.add (Calendar.YEAR, 2);
        System.out.println ("2 years later: " + calendar.getTime ());
    }
}

Output

Program for Java Calendar Class

Sample Program
import java.util.*;
public class CalendarDemo2
{
    public static void main (String[]args)
    {
        Calendar calendar = Calendar.getInstance ();
        System.out.println ("At present Calendar's Year: " + calendar.get (Calendar.YEAR));
        System.out.println ("At present Calendar's Day: " + calendar.get (Calendar.DATE));
        System.out.print ("At present Date And Time Is: " + calendar.getTime ());
        int maximum = calendar.getMaximum (Calendar.DAY_OF_WEEK);
        System.out.println ("Maximum number of days in week: " + maximum);
        maximum = calendar.getMaximum (Calendar.WEEK_OF_YEAR);
        System.out.println ("Maximum number of weeks in year: " + maximum);
        int minimum = calendar.getMinimum (Calendar.DAY_OF_WEEK);
        System.out.println ("Minimum number of days in week: " + minimum);
        minimum = calendar.getMinimum (Calendar.WEEK_OF_YEAR);
        System.out.println ("Minimum number of weeks in year: " + minimum);
    }
}

Output

Java Calendar Class with Examples

In the next article, I am going to discuss System.Exit Method in Java with Examples. Here, in this article, I try to explain Java Calendar Class with Examples. I hope you enjoy this Java Calendar Class with Examples article.

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