(a)Write the definitions of the methods of the class Calendar to implement the o
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(a)Write the definitions of the methods of the class Calendar to implement the operations of the class Calendar. (b) Write a test program to print the calendar for either a particular month or a particular year.Explanation / Answer
Method Detail getInstance public static Calendar getInstance() Gets a calendar using the default time zone and locale. The Calendar returned is based on the current time in the default time zone with the default locale. Returns: a Calendar. getInstance public static Calendar getInstance(TimeZone zone) Gets a calendar using the specified time zone and default locale. The Calendar returned is based on the current time in the given time zone with the default locale. Parameters: zone - the time zone to use Returns: a Calendar. getInstance public static Calendar getInstance(Locale aLocale) Gets a calendar using the default time zone and specified locale. The Calendar returned is based on the current time in the default time zone with the given locale. Parameters: aLocale - the locale for the week data Returns: a Calendar. getInstance public static Calendar getInstance(TimeZone zone, Locale aLocale) Gets a calendar with the specified time zone and locale. The Calendar returned is based on the current time in the given time zone with the given locale. Parameters: zone - the time zone to use aLocale - the locale for the week data Returns: a Calendar. getAvailableLocales public static Locale[] getAvailableLocales() Returns an array of all locales for which the getInstance methods of this class can return localized instances. The array returned must contain at least a Locale instance equal to Locale.US. Returns: An array of locales for which localized Calendar instances are available. computeTime protected abstract void computeTime() Converts the current calendar field values in fields[] to the millisecond time value time. See Also: complete(), computeFields() computeFields protected abstract void computeFields() Converts the current millisecond time value time to calendar field values in fields[]. This allows you to sync up the calendar field values with a new time that is set for the calendar. The time is not recomputed first; to recompute the time, then the fields, call the complete() method. See Also: computeTime() getTime public final Date getTime() Returns a Date object representing this Calendar's time value (millisecond offset from the Epoch"). Returns: a Date representing the time value. See Also: setTime(Date), getTimeInMillis() setTime public final void setTime(Date date) Sets this Calendar's time with the given Date. Note: Calling setTime() with Date(Long.MAX_VALUE) or Date(Long.MIN_VALUE) may yield incorrect field values from get(). Parameters: date - the given Date. See Also: getTime(), setTimeInMillis(long) getTimeInMillis public long getTimeInMillis() Returns this Calendar's time value in milliseconds. Returns: the current time as UTC milliseconds from the epoch. See Also: getTime(), setTimeInMillis(long) setTimeInMillis public void setTimeInMillis(long millis) Sets this Calendar's current time from the given long value. Parameters: millis - the new time in UTC milliseconds from the epoch. See Also: setTime(Date), getTimeInMillis() get public int get(int field) Returns the value of the given calendar field. In lenient mode, all calendar fields are normalized. In non-lenient mode, all calendar fields are validated and this method throws an exception if any calendar fields have out-of-range values. The normalization and validation are handled by the complete() method, which process is calendar system dependent. Parameters: field - the given calendar field. Returns: the value for the given calendar field. Throws: ArrayIndexOutOfBoundsException - if the specified field is out of range (field < 0 || field >= FIELD_COUNT). See Also: set(int,int), complete() internalGet protected final int internalGet(int field) Returns the value of the given calendar field. This method does not involve normalization or validation of the field value. Parameters: field - the given calendar field. Returns: the value for the given calendar field. See Also: get(int) set public void set(int field, int value) Sets the given calendar field to the given value. The value is not interpreted by this method regardless of the leniency mode. Parameters: field - the given calendar field. value - the value to be set for the given calendar field. Throws: ArrayIndexOutOfBoundsException - if the specified field is out of range (field < 0 || field >= FIELD_COUNT). in non-lenient mode. See Also: set(int,int,int), set(int,int,int,int,int), set(int,int,int,int,int,int), get(int) set public final void set(int year, int month, int date) Sets the values for the calendar fields YEAR, MONTH, and DAY_OF_MONTH. Previous values of other calendar fields are retained. If this is not desired, call clear() first. Parameters: year - the value used to set the YEAR calendar field. month - the value used to set the MONTH calendar field. Month value is 0-based. e.g., 0 for January. date - the value used to set the DAY_OF_MONTH calendar field. See Also: set(int,int), set(int,int,int,int,int), set(int,int,int,int,int,int) set public final void set(int year, int month, int date, int hourOfDay, int minute) Sets the values for the calendar fields YEAR, MONTH, DAY_OF_MONTH, HOUR_OF_DAY, and MINUTE. Previous values of other fields are retained. If this is not desired, call clear() first. Parameters: year - the value used to set the YEAR calendar field. month - the value used to set the MONTH calendar field. Month value is 0-based. e.g., 0 for January. date - the value used to set the DAY_OF_MONTH calendar field. hourOfDay - the value used to set the HOUR_OF_DAY calendar field. minute - the value used to set the MINUTE calendar field. See Also: set(int,int), set(int,int,int), set(int,int,int,int,int,int) set public final void set(int year, int month, int date, int hourOfDay, int minute, int second) Sets the values for the fields YEAR, MONTH, DAY_OF_MONTH, HOUR, MINUTE, and SECOND. Previous values of other fields are retained. If this is not desired, call clear() first. Parameters: year - the value used to set the YEAR calendar field. month - the value used to set the MONTH calendar field. Month value is 0-based. e.g., 0 for January. date - the value used to set the DAY_OF_MONTH calendar field. hourOfDay - the value used to set the HOUR_OF_DAY calendar field. minute - the value used to set the MINUTE calendar field. second - the value used to set the SECOND calendar field. See Also: set(int,int), set(int,int,int), set(int,int,int,int,int) clear public final void clear() Sets all the calendar field values and the time value (millisecond offset from the Epoch) of this Calendar undefined. This means that isSet() will return false for all the calendar fields, and the date and time calculations will treat the fields as if they had never been set. A Calendar implementation class may use its specific default field values for date/time calculations. For example, GregorianCalendar uses 1970 if the YEAR field value is undefined. See Also: clear(int) clear public final void clear(int field) Sets the given calendar field value and the time value (millisecond offset from the Epoch) of this Calendar undefined. This means that isSet(field) will return false, and the date and time calculations will treat the field as if it had never been set. A Calendar implementation class may use the field's specific default value for date and time calculations. The HOUR_OF_DAY, HOUR and AM_PM fields are handled independently and the the resolution rule for the time of day is applied. Clearing one of the fields doesn't reset the hour of day value of this Calendar. Use set(Calendar.HOUR_OF_DAY, 0) to reset the hour value. Parameters: field - the calendar field to be cleared. See Also: clear() isSet public final boolean isSet(int field) Determines if the given calendar field has a value set, including cases that the value has been set by internal fields calculations triggered by a get method call. Returns: true if the given calendar field has a value set; false otherwise. getDisplayName public String getDisplayName(int field, int style, Locale locale) Returns the string representation of the calendar field value in the given style and locale. If no string representation is applicable, null is returned. This method calls get(field) to get the calendar field value if the string representation is applicable to the given calendar field. For example, if this Calendar is a GregorianCalendar and its date is 2005-01-01, then the string representation of the MONTH field would be "January" in the long style in an English locale or "Jan" in the short style. However, no string representation would be available for the DAY_OF_MONTH field, and this method would return null. The default implementation supports the calendar fields for which a DateFormatSymbols has names in the given locale. Parameters: field - the calendar field for which the string representation is returned style - the style applied to the string representation; one of SHORT or LONG. locale - the locale for the string representation Returns: the string representation of the given field in the given style, or null if no string representation is applicable. Throws: IllegalArgumentException - if field or style is invalid, or if this Calendar is non-lenient and any of the calendar fields have invalid values NullPointerException - if locale is null Since: 1.6 getDisplayNames public Map getDisplayNames(int field, int style, Locale locale) Returns a Map containing all names of the calendar field in the given style and locale and their corresponding field values. For example, if this Calendar is a GregorianCalendar, the returned map would contain "Jan" to JANUARY, "Feb" to FEBRUARY, and so on, in the short style in an English locale. The values of other calendar fields may be taken into account to determine a set of display names. For example, if this Calendar is a lunisolar calendar system and the year value given by the YEAR field has a leap month, this method would return month names containing the leap month name, and month names are mapped to their values specific for the year. The default implementation supports display names contained in a DateFormatSymbols. For example, if field is MONTH and style is ALL_STYLES, this method returns a Map containing all strings returned by DateFormatSymbols.getShortMonths() and DateFormatSymbols.getMonths(). Parameters: field - the calendar field for which the display names are returned style - the style applied to the display names; one of SHORT, LONG, or ALL_STYLES. locale - the locale for the display names Returns: a Map containing all display names in style and locale and their field values, or null if no display names are defined for field Throws: IllegalArgumentException - if field or style is invalid, or if this Calendar is non-lenient and any of the calendar fields have invalid values NullPointerException - if locale is null Since: 1.6 complete protected void complete() Fills in any unset fields in the calendar fields. First, the computeTime() method is called if the time value (millisecond offset from the Epoch) has not been calculated from calendar field values. Then, the computeFields() method is called to calculate all calendar field values. equals public boolean equals(Object obj) Compares this Calendar to the specified Object. The result is true if and only if the argument is a Calendar object of the same calendar system that represents the same time value (millisecond offset from the Epoch) under the same Calendar parameters as this object. The Calendar parameters are the values represented by the isLenient, getFirstDayOfWeek, getMinimalDaysInFirstWeek and getTimeZone methods. If there is any difference in those parameters between the two Calendars, this method returns false. Use the compareTo method to compare only the time values. Overrides: equals in class Object Parameters: obj - the object to compare with. Returns: true if this object is equal to obj; false otherwise. See Also: Object.hashCode(), Hashtable hashCode public int hashCode() Returns a hash code for this calendar. Overrides: hashCode in class Object Returns: a hash code value for this object. Since: 1.2 See Also: Object.equals(java.lang.Object), Hashtable before public boolean before(Object when) Returns whether this Calendar represents a time before the time represented by the specified Object. This method is equivalent to: compareTo(when) < 0 if and only if when is a Calendar instance. Otherwise, the method returns false. Parameters: when - the Object to be compared Returns: true if the time of this Calendar is before the time represented by when; false otherwise. See Also: compareTo(Calendar) after public boolean after(Object when) Returns whether this Calendar represents a time after the time represented by the specified Object. This method is equivalent to: compareTo(when) > 0 if and only if when is a Calendar instance. Otherwise, the method returns false. Parameters: when - the Object to be compared Returns: true if the time of this Calendar is after the time represented by when; false otherwise. See Also: compareTo(Calendar) compareTo public int compareTo(Calendar anotherCalendar) Compares the time values (millisecond offsets from the Epoch) represented by two Calendar objects. Specified by: compareTo in interface Comparable Parameters: anotherCalendar - the Calendar to be compared. Returns: the value 0 if the time represented by the argument is equal to the time represented by this Calendar; a value less than 0 if the time of this Calendar is before the time represented by the argument; and a value greater than 0 if the time of this Calendar is after the time represented by the argument. Throws: NullPointerException - if the specified Calendar is null. IllegalArgumentException - if the time value of the specified Calendar object can't be obtained due to any invalid calendar values. Since: 1.5 add public abstract void add(int field, int amount) Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling: add(Calendar.DAY_OF_MONTH, -5). Parameters: field - the calendar field. amount - the amount of date or time to be added to the field. See Also: roll(int,int), set(int,int) roll public abstract void roll(int field, boolean up) Adds or subtracts (up/down) a single unit of time on the given time field without changing larger fields. For example, to roll the current date up by one day, you can achieve it by calling: roll(Calendar.DATE, true). When rolling on the year or Calendar.YEAR field, it will roll the year value in the range between 1 and the value returned by calling getMaximum(Calendar.YEAR). When rolling on the month or Calendar.MONTH field, other fields like date might conflict and, need to be changed. For instance, rolling the month on the date 01/31/96 will result in 02/29/96. When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will roll the hour value in the range between 0 and 23, which is zero-based. Parameters: field - the time field. up - indicates if the value of the specified time field is to be rolled up or rolled down. Use true if rolling up, false otherwise. See Also: add(int,int), set(int,int) roll public void roll(int field, int amount) Adds the specified (signed) amount to the specified calendar field without changing larger fields. A negative amount means to roll down. NOTE: This default implementation on Calendar just repeatedly calls the version of roll() that rolls by one unit. This may not always do the right thing. For example, if the DAY_OF_MONTH field is 31, rolling through February will leave it set to 28. The GregorianCalendar version of this function takes care of this problem. Other subclasses should also provide overrides of this function that do the right thing. Parameters: field - the calendar field. amount - the signed amount to add to the calendar field. Since: 1.2 See Also: roll(int,boolean), add(int,int), set(int,int) setTimeZone public void setTimeZone(TimeZone value) Sets the time zone with the given time zone value. Parameters: value - the given time zone. getTimeZone public TimeZone getTimeZone() Gets the time zone. Returns: the time zone object associated with this calendar. setLenient public void setLenient(boolean lenient) Specifies whether or not date/time interpretation is to be lenient. With lenient interpretation, a date such as "February 942, 1996" will be treated as being equivalent to the 941st day after February 1, 1996. With strict (non-lenient) interpretation, such dates will cause an exception to be thrown. The default is lenient. Parameters: lenient - true if the lenient mode is to be turned on; false if it is to be turned off. See Also: isLenient(), DateFormat.setLenient(boolean) isLenient public boolean isLenient() Tells whether date/time interpretation is to be lenient. Returns: true if the interpretation mode of this calendar is lenient; false otherwise. See Also: setLenient(boolean) setFirstDayOfWeek public void setFirstDayOfWeek(int value) Sets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France. Parameters: value - the given first day of the week. See Also: getFirstDayOfWeek(), getMinimalDaysInFirstWeek() getFirstDayOfWeek public int getFirstDayOfWeek() Gets what the first day of the week is; e.g., SUNDAY in the U.S., MONDAY in France. Returns: the first day of the week. See Also: setFirstDayOfWeek(int), getMinimalDaysInFirstWeek() setMinimalDaysInFirstWeek public void setMinimalDaysInFirstWeek(int value) Sets what the minimal days required in the first week of the year are; For example, if the first week is defined as one that contains the first day of the first month of a year, call this method with value 1. If it must be a full week, use value 7. Parameters: value - the given minimal days required in the first week of the year. See Also: getMinimalDaysInFirstWeek() getMinimalDaysInFirstWeek public int getMinimalDaysInFirstWeek() Gets what the minimal days required in the first week of the year are; e.g., if the first week is defined as one that contains the first day of the first month of a year, this method returns 1. If the minimal days required must be a full week, this method returns 7. Returns: the minimal days required in the first week of the year. See Also: setMinimalDaysInFirstWeek(int) getMinimum public abstract int getMinimum(int field) Returns the minimum value for the given calendar field of this Calendar instance. The minimum value is defined as the smallest value returned by the get method for any possible time value. The minimum value depends on calendar system specific parameters of the instance. Parameters: field - the calendar field. Returns: the minimum value for the given calendar field. See Also: getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int) getMaximum public abstract int getMaximum(int field) Returns the maximum value for the given calendar field of this Calendar instance. The maximum value is defined as the largest value returned by the get method for any possible time value. The maximum value depends on calendar system specific parameters of the instance. Parameters: field - the calendar field. Returns: the maximum value for the given calendar field. See Also: getMinimum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int) getGreatestMinimum public abstract int getGreatestMinimum(int field) Returns the highest minimum value for the given calendar field of this Calendar instance. The highest minimum value is defined as the largest value returned by getActualMinimum(int) for any possible time value. The greatest minimum value depends on calendar system specific parameters of the instance. Parameters: field - the calendar field. Returns: the highest minimum value for the given calendar field. See Also: getMinimum(int), getMaximum(int), getLeastMaximum(int), getActualMinimum(int), getActualMaximum(int) getLeastMaximum public abstract int getLeastMaximum(int field) Returns the lowest maximum value for the given calendar field of this Calendar instance. The lowest maximum value is defined as the smallest value returned by getActualMaximum(int) for any possible time value. The least maximum value depends on calendar system specific parameters of the instance. For example, a Calendar for the Gregorian calendar system returns 28 for the DAY_OF_MONTH field, because the 28th is the last day of the shortest month of this calendar, February in a common year. Parameters: field - the calendar field. Returns: the lowest maximum value for the given calendar field. See Also: getMinimum(int), getMaximum(int), getGreatestMinimum(int), getActualMinimum(int), getActualMaximum(int) getActualMinimum public int getActualMinimum(int field) Returns the minimum value that the specified calendar field could have, given the time value of this Calendar. The default implementation of this method uses an iterative algorithm to determine the actual minimum value for the calendar field. Subclasses should, if possible, override this with a more efficient implementation - in many cases, they can simply return getMinimum(). Parameters: field - the calendar field Returns: the minimum of the given calendar field for the time value of this Calendar Since: 1.2 See Also: getMinimum(int), getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMaximum(int) getActualMaximum public int getActualMaximum(int field) Returns the maximum value that the specified calendar field could have, given the time value of this Calendar. For example, the actual maximum value of the MONTH field is 12 in some years, and 13 in other years in the Hebrew calendar system. The default implementation of this method uses an iterative algorithm to determine the actual maximum value for the calendar field. Subclasses should, if possible, override this with a more efficient implementation. Parameters: field - the calendar field Returns: the maximum of the given calendar field for the time value of this Calendar Since: 1.2 See Also: getMinimum(int), getMaximum(int), getGreatestMinimum(int), getLeastMaximum(int), getActualMinimum(int) clone public Object clone() Creates and returns a copy of this object. Overrides: clone in class Object Returns: a copy of this object. See Also: Cloneable toString public String toString() Return a string representation of this calendar. This method is intended to be used only for debugging purposes, and the format of the returned string may vary between implementations. The returned string may be empty but may not be null. Overrides: toString in class Object Returns: a string representation of this calendar.Related Questions
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