Class SerialDate

  • All Implemented Interfaces:
    Serializable, Comparable, MonthConstants
    Direct Known Subclasses:
    SpreadsheetDate

    public abstract class SerialDate
    extends Object
    implements Comparable, Serializable, MonthConstants
    An abstract class that defines our requirements for manipulating dates, without tying down a particular implementation.

    Requirement 1 : match at least what Excel does for dates; Requirement 2 : the date represented by the class is immutable;

    Why not just use java.util.Date? We will, when it makes sense. At times, java.util.Date can be *too* precise - it represents an instant in time, accurate to 1/1000th of a second (with the date itself depending on the time-zone). Sometimes we just want to represent a particular day (e.g. 21 January 2015) without concerning ourselves about the time of day, or the time-zone, or anything else. That's what we've defined SerialDate for.

    You can call getInstance() to get a concrete subclass of SerialDate, without worrying about the exact implementation.

    Author:
    David Gilbert
    See Also:
    Serialized Form
    • Field Detail

      • DATE_FORMAT_SYMBOLS

        public static final DateFormatSymbols DATE_FORMAT_SYMBOLS
        Date format symbols.
      • SERIAL_LOWER_BOUND

        public static final int SERIAL_LOWER_BOUND
        The serial number for 1 January 1900.
        See Also:
        Constant Field Values
      • SERIAL_UPPER_BOUND

        public static final int SERIAL_UPPER_BOUND
        The serial number for 31 December 9999.
        See Also:
        Constant Field Values
      • MINIMUM_YEAR_SUPPORTED

        public static final int MINIMUM_YEAR_SUPPORTED
        The lowest year value supported by this date format.
        See Also:
        Constant Field Values
      • MAXIMUM_YEAR_SUPPORTED

        public static final int MAXIMUM_YEAR_SUPPORTED
        The highest year value supported by this date format.
        See Also:
        Constant Field Values
      • MONDAY

        public static final int MONDAY
        Useful constant for Monday. Equivalent to java.util.Calendar.MONDAY.
        See Also:
        Constant Field Values
      • TUESDAY

        public static final int TUESDAY
        Useful constant for Tuesday. Equivalent to java.util.Calendar.TUESDAY.
        See Also:
        Constant Field Values
      • WEDNESDAY

        public static final int WEDNESDAY
        Useful constant for Wednesday. Equivalent to java.util.Calendar.WEDNESDAY.
        See Also:
        Constant Field Values
      • THURSDAY

        public static final int THURSDAY
        Useful constant for Thrusday. Equivalent to java.util.Calendar.THURSDAY.
        See Also:
        Constant Field Values
      • FRIDAY

        public static final int FRIDAY
        Useful constant for Friday. Equivalent to java.util.Calendar.FRIDAY.
        See Also:
        Constant Field Values
      • SATURDAY

        public static final int SATURDAY
        Useful constant for Saturday. Equivalent to java.util.Calendar.SATURDAY.
        See Also:
        Constant Field Values
      • SUNDAY

        public static final int SUNDAY
        Useful constant for Sunday. Equivalent to java.util.Calendar.SUNDAY.
        See Also:
        Constant Field Values
      • FIRST_WEEK_IN_MONTH

        public static final int FIRST_WEEK_IN_MONTH
        A useful constant for referring to the first week in a month.
        See Also:
        Constant Field Values
      • SECOND_WEEK_IN_MONTH

        public static final int SECOND_WEEK_IN_MONTH
        A useful constant for referring to the second week in a month.
        See Also:
        Constant Field Values
      • THIRD_WEEK_IN_MONTH

        public static final int THIRD_WEEK_IN_MONTH
        A useful constant for referring to the third week in a month.
        See Also:
        Constant Field Values
      • FOURTH_WEEK_IN_MONTH

        public static final int FOURTH_WEEK_IN_MONTH
        A useful constant for referring to the fourth week in a month.
        See Also:
        Constant Field Values
      • LAST_WEEK_IN_MONTH

        public static final int LAST_WEEK_IN_MONTH
        A useful constant for referring to the last week in a month.
        See Also:
        Constant Field Values
      • INCLUDE_NONE

        public static final int INCLUDE_NONE
        Useful range constant.
        See Also:
        Constant Field Values
      • INCLUDE_FIRST

        public static final int INCLUDE_FIRST
        Useful range constant.
        See Also:
        Constant Field Values
      • INCLUDE_SECOND

        public static final int INCLUDE_SECOND
        Useful range constant.
        See Also:
        Constant Field Values
      • INCLUDE_BOTH

        public static final int INCLUDE_BOTH
        Useful range constant.
        See Also:
        Constant Field Values
      • PRECEDING

        public static final int PRECEDING
        Useful constant for specifying a day of the week relative to a fixed date.
        See Also:
        Constant Field Values
      • NEAREST

        public static final int NEAREST
        Useful constant for specifying a day of the week relative to a fixed date.
        See Also:
        Constant Field Values
      • FOLLOWING

        public static final int FOLLOWING
        Useful constant for specifying a day of the week relative to a fixed date.
        See Also:
        Constant Field Values
    • Constructor Detail

      • SerialDate

        protected SerialDate()
        Default constructor.
    • Method Detail

      • isValidWeekdayCode

        public static boolean isValidWeekdayCode​(int code)
        Returns true if the supplied integer code represents a valid day-of-the-week, and false otherwise.
        Parameters:
        code - the code being checked for validity.
        Returns:
        true if the supplied integer code represents a valid day-of-the-week, and false otherwise.
      • stringToWeekdayCode

        public static int stringToWeekdayCode​(String s)
        Converts the supplied string to a day of the week.
        Parameters:
        s - a string representing the day of the week.
        Returns:
        -1 if the string is not convertable, the day of the week otherwise.
      • weekdayCodeToString

        public static String weekdayCodeToString​(int weekday)
        Returns a string representing the supplied day-of-the-week.

        Need to find a better approach.

        Parameters:
        weekday - the day of the week.
        Returns:
        a string representing the supplied day-of-the-week.
      • getMonths

        public static String[] getMonths()
        Returns an array of month names.
        Returns:
        an array of month names.
      • getMonths

        public static String[] getMonths​(boolean shortened)
        Returns an array of month names.
        Parameters:
        shortened - a flag indicating that shortened month names should be returned.
        Returns:
        an array of month names.
      • isValidMonthCode

        public static boolean isValidMonthCode​(int code)
        Returns true if the supplied integer code represents a valid month.
        Parameters:
        code - the code being checked for validity.
        Returns:
        true if the supplied integer code represents a valid month.
      • monthCodeToQuarter

        public static int monthCodeToQuarter​(int code)
        Returns the quarter for the specified month.
        Parameters:
        code - the month code (1-12).
        Returns:
        the quarter that the month belongs to.
      • monthCodeToString

        public static String monthCodeToString​(int month)
        Returns a string representing the supplied month.

        The string returned is the long form of the month name taken from the default locale.

        Parameters:
        month - the month.
        Returns:
        a string representing the supplied month.
      • monthCodeToString

        public static String monthCodeToString​(int month,
                                               boolean shortened)
        Returns a string representing the supplied month.

        The string returned is the long or short form of the month name taken from the default locale.

        Parameters:
        month - the month.
        shortened - if true return the abbreviation of the month.
        Returns:
        a string representing the supplied month.
      • stringToMonthCode

        public static int stringToMonthCode​(String s)
        Converts a string to a month code.

        This method will return one of the constants JANUARY, FEBRUARY, ..., DECEMBER that corresponds to the string. If the string is not recognised, this method returns -1.

        Parameters:
        s - the string to parse.
        Returns:
        -1 if the string is not parseable, the month of the year otherwise.
      • isValidWeekInMonthCode

        public static boolean isValidWeekInMonthCode​(int code)
        Returns true if the supplied integer code represents a valid week-in-the-month, and false otherwise.
        Parameters:
        code - the code being checked for validity.
        Returns:
        true if the supplied integer code represents a valid week-in-the-month.
      • isLeapYear

        public static boolean isLeapYear​(int yyyy)
        Determines whether or not the specified year is a leap year.
        Parameters:
        yyyy - the year (in the range 1900 to 9999).
        Returns:
        true if the specified year is a leap year.
      • leapYearCount

        public static int leapYearCount​(int yyyy)
        Returns the number of leap years from 1900 to the specified year INCLUSIVE.

        Note that 1900 is not a leap year.

        Parameters:
        yyyy - the year (in the range 1900 to 9999).
        Returns:
        the number of leap years from 1900 to the specified year.
      • lastDayOfMonth

        public static int lastDayOfMonth​(int month,
                                         int yyyy)
        Returns the number of the last day of the month, taking into account leap years.
        Parameters:
        month - the month.
        yyyy - the year (in the range 1900 to 9999).
        Returns:
        the number of the last day of the month.
      • addDays

        public static SerialDate addDays​(int days,
                                         SerialDate base)
        Creates a new date by adding the specified number of days to the base date.
        Parameters:
        days - the number of days to add (can be negative).
        base - the base date.
        Returns:
        a new date.
      • addMonths

        public static SerialDate addMonths​(int months,
                                           SerialDate base)
        Creates a new date by adding the specified number of months to the base date.

        If the base date is close to the end of the month, the day on the result may be adjusted slightly: 31 May + 1 month = 30 June.

        Parameters:
        months - the number of months to add (can be negative).
        base - the base date.
        Returns:
        a new date.
      • addYears

        public static SerialDate addYears​(int years,
                                          SerialDate base)
        Creates a new date by adding the specified number of years to the base date.
        Parameters:
        years - the number of years to add (can be negative).
        base - the base date.
        Returns:
        A new date.
      • getPreviousDayOfWeek

        public static SerialDate getPreviousDayOfWeek​(int targetWeekday,
                                                      SerialDate base)
        Returns the latest date that falls on the specified day-of-the-week and is BEFORE the base date.
        Parameters:
        targetWeekday - a code for the target day-of-the-week.
        base - the base date.
        Returns:
        the latest date that falls on the specified day-of-the-week and is BEFORE the base date.
      • getFollowingDayOfWeek

        public static SerialDate getFollowingDayOfWeek​(int targetWeekday,
                                                       SerialDate base)
        Returns the earliest date that falls on the specified day-of-the-week and is AFTER the base date.
        Parameters:
        targetWeekday - a code for the target day-of-the-week.
        base - the base date.
        Returns:
        the earliest date that falls on the specified day-of-the-week and is AFTER the base date.
      • getNearestDayOfWeek

        public static SerialDate getNearestDayOfWeek​(int targetDOW,
                                                     SerialDate base)
        Returns the date that falls on the specified day-of-the-week and is CLOSEST to the base date.
        Parameters:
        targetDOW - a code for the target day-of-the-week.
        base - the base date.
        Returns:
        the date that falls on the specified day-of-the-week and is CLOSEST to the base date.
      • getEndOfCurrentMonth

        public SerialDate getEndOfCurrentMonth​(SerialDate base)
        Rolls the date forward to the last day of the month.
        Parameters:
        base - the base date.
        Returns:
        a new serial date.
      • weekInMonthToString

        public static String weekInMonthToString​(int count)
        Returns a string corresponding to the week-in-the-month code.

        Need to find a better approach.

        Parameters:
        count - an integer code representing the week-in-the-month.
        Returns:
        a string corresponding to the week-in-the-month code.
      • relativeToString

        public static String relativeToString​(int relative)
        Returns a string representing the supplied 'relative'.

        Need to find a better approach.

        Parameters:
        relative - a constant representing the 'relative'.
        Returns:
        a string representing the supplied 'relative'.
      • createInstance

        public static SerialDate createInstance​(int day,
                                                int month,
                                                int yyyy)
        Factory method that returns an instance of some concrete subclass of SerialDate.
        Parameters:
        day - the day (1-31).
        month - the month (1-12).
        yyyy - the year (in the range 1900 to 9999).
        Returns:
        An instance of SerialDate.
      • createInstance

        public static SerialDate createInstance​(int serial)
        Factory method that returns an instance of some concrete subclass of SerialDate.
        Parameters:
        serial - the serial number for the day (1 January 1900 = 2).
        Returns:
        a instance of SerialDate.
      • createInstance

        public static SerialDate createInstance​(Date date)
        Factory method that returns an instance of a subclass of SerialDate.
        Parameters:
        date - A Java date object.
        Returns:
        a instance of SerialDate.
      • toSerial

        public abstract int toSerial()
        Returns the serial number for the date, where 1 January 1900 = 2 (this corresponds, almost, to the numbering system used in Microsoft Excel for Windows and Lotus 1-2-3).
        Returns:
        the serial number for the date.
      • toDate

        public abstract Date toDate()
        Returns a java.util.Date. Since java.util.Date has more precision than SerialDate, we need to define a convention for the 'time of day'.
        Returns:
        this as java.util.Date.
      • getDescription

        public String getDescription()
        Returns the description that is attached to the date. It is not required that a date have a description, but for some applications it is useful.
        Returns:
        The description (possibly null).
      • setDescription

        public void setDescription​(String description)
        Sets the description for the date.
        Parameters:
        description - the description for this date (null permitted).
      • toString

        public String toString()
        Converts the date to a string.
        Overrides:
        toString in class Object
        Returns:
        a string representation of the date.
      • getYYYY

        public abstract int getYYYY()
        Returns the year (assume a valid range of 1900 to 9999).
        Returns:
        the year.
      • getMonth

        public abstract int getMonth()
        Returns the month (January = 1, February = 2, March = 3).
        Returns:
        the month of the year.
      • getDayOfMonth

        public abstract int getDayOfMonth()
        Returns the day of the month.
        Returns:
        the day of the month.
      • getDayOfWeek

        public abstract int getDayOfWeek()
        Returns the day of the week.
        Returns:
        the day of the week.
      • compare

        public abstract int compare​(SerialDate other)
        Returns the difference (in days) between this date and the specified 'other' date.

        The result is positive if this date is after the 'other' date and negative if it is before the 'other' date.

        Parameters:
        other - the date being compared to.
        Returns:
        the difference between this and the other date.
      • isOn

        public abstract boolean isOn​(SerialDate other)
        Returns true if this SerialDate represents the same date as the specified SerialDate.
        Parameters:
        other - the date being compared to.
        Returns:
        true if this SerialDate represents the same date as the specified SerialDate.
      • isBefore

        public abstract boolean isBefore​(SerialDate other)
        Returns true if this SerialDate represents an earlier date compared to the specified SerialDate.
        Parameters:
        other - The date being compared to.
        Returns:
        true if this SerialDate represents an earlier date compared to the specified SerialDate.
      • isOnOrBefore

        public abstract boolean isOnOrBefore​(SerialDate other)
        Returns true if this SerialDate represents the same date as the specified SerialDate.
        Parameters:
        other - the date being compared to.
        Returns:
        true if this SerialDate represents the same date as the specified SerialDate.
      • isAfter

        public abstract boolean isAfter​(SerialDate other)
        Returns true if this SerialDate represents the same date as the specified SerialDate.
        Parameters:
        other - the date being compared to.
        Returns:
        true if this SerialDate represents the same date as the specified SerialDate.
      • isOnOrAfter

        public abstract boolean isOnOrAfter​(SerialDate other)
        Returns true if this SerialDate represents the same date as the specified SerialDate.
        Parameters:
        other - the date being compared to.
        Returns:
        true if this SerialDate represents the same date as the specified SerialDate.
      • isInRange

        public abstract boolean isInRange​(SerialDate d1,
                                          SerialDate d2)
        Returns true if this SerialDate is within the specified range (INCLUSIVE). The date order of d1 and d2 is not important.
        Parameters:
        d1 - a boundary date for the range.
        d2 - the other boundary date for the range.
        Returns:
        A boolean.
      • isInRange

        public abstract boolean isInRange​(SerialDate d1,
                                          SerialDate d2,
                                          int include)
        Returns true if this SerialDate is within the specified range (caller specifies whether or not the end-points are included). The date order of d1 and d2 is not important.
        Parameters:
        d1 - a boundary date for the range.
        d2 - the other boundary date for the range.
        include - a code that controls whether or not the start and end dates are included in the range.
        Returns:
        A boolean.
      • getPreviousDayOfWeek

        public SerialDate getPreviousDayOfWeek​(int targetDOW)
        Returns the latest date that falls on the specified day-of-the-week and is BEFORE this date.
        Parameters:
        targetDOW - a code for the target day-of-the-week.
        Returns:
        the latest date that falls on the specified day-of-the-week and is BEFORE this date.
      • getFollowingDayOfWeek

        public SerialDate getFollowingDayOfWeek​(int targetDOW)
        Returns the earliest date that falls on the specified day-of-the-week and is AFTER this date.
        Parameters:
        targetDOW - a code for the target day-of-the-week.
        Returns:
        the earliest date that falls on the specified day-of-the-week and is AFTER this date.
      • getNearestDayOfWeek

        public SerialDate getNearestDayOfWeek​(int targetDOW)
        Returns the nearest date that falls on the specified day-of-the-week.
        Parameters:
        targetDOW - a code for the target day-of-the-week.
        Returns:
        the nearest date that falls on the specified day-of-the-week.