month.java

java图形利器

            }
        }
        return result;
    }

    /**
     * Returns a serial index number for the month.
     *
     * @return The serial index number.
     */
    public long getSerialIndex() {
        return this.year * 12L + this.month;
    }

    /**
     * Returns a string representing the month (e.g. "January 2002").
     * <P>
     * To do: look at internationalisation.
     *
     * @return A string representing the month.
     */
    public String toString() {
        return SerialDate.monthCodeToString(this.month) + " " + this.year;
    }

    /**
     * Tests the equality of this Month object to an arbitrary object.
     * Returns true if the target is a Month instance representing the same
     * month as this object.  In all other cases, returns false.
     *
     * @param obj  the object (<code>null</code> permitted).
     *
     * @return <code>true</code> if month and year of this and object are the 
     *         same.
     */
    public boolean equals(Object obj) {

        if (obj != null) {
            if (obj instanceof Month) {
                Month target = (Month) obj;
                return (this.month == target.getMonth() 
                        && (this.year == target.getYearValue()));
            }
            else {
                return false;
            }
        }
        else {
            return false;
        }

    }

    /**
     * Returns a hash code for this object instance.  The approach described by
     * Joshua Bloch in "Effective Java" has been used here:
     * <p>
     * <code>http://developer.java.sun.com/developer/Books/effectivejava
     * /Chapter3.pdf</code>
     * 
     * @return A hash code.
     */
    public int hashCode() {
        int result = 17;
        result = 37 * result + this.month;
        result = 37 * result + this.year;
        return result;
    }

    /**
     * Returns an integer indicating the order of this Month object relative to
     * the specified
     * object: negative == before, zero == same, positive == after.
     *
     * @param o1  the object to compare.
     *
     * @return negative == before, zero == same, positive == after.
     */
    public int compareTo(Object o1) {

        int result;

        // CASE 1 : Comparing to another Month object
        // --------------------------------------------
        if (o1 instanceof Month) {
            Month m = (Month) o1;
            result = this.year - m.getYearValue();
            if (result == 0) {
                result = this.month - m.getMonth();
            }
        }

        // CASE 2 : Comparing to another TimePeriod object
        // -----------------------------------------------
        else if (o1 instanceof RegularTimePeriod) {
            // more difficult case - evaluate later...
            result = 0;
        }

        // CASE 3 : Comparing to a non-TimePeriod object
        // ---------------------------------------------
        else {
            // consider time periods to be ordered after general objects
            result = 1;
        }

        return result;

    }

    /**
     * Returns the first millisecond of the month, evaluated using the supplied
     * calendar (which determines the time zone).
     *
     * @param calendar  the calendar (<code>null</code> not permitted).
     *
     * @return The first millisecond of the month.
     *
     * @throws NullPointerException if <code>calendar</code> is 
     *     <code>null</code>.
     */
    public long getFirstMillisecond(Calendar calendar) {
        calendar.set(this.year, this.month - 1, 1, 0, 0, 0);
        calendar.set(Calendar.MILLISECOND, 0);
        // in the following line, we'd rather call calendar.getTimeInMillis()
        // to avoid object creation, but that isn't supported in Java 1.3.1
        return calendar.getTime().getTime();
    }

    /**
     * Returns the last millisecond of the month, evaluated using the supplied
     * calendar (which determines the time zone).
     *
     * @param calendar  the calendar (<code>null</code> not permitted).
     *
     * @return The last millisecond of the month.
     *
     * @throws NullPointerException if <code>calendar</code> is 
     *     <code>null</code>.
     */
    public long getLastMillisecond(Calendar calendar) {
        int eom = SerialDate.lastDayOfMonth(this.month, this.year);
        calendar.set(this.year, this.month - 1, eom, 23, 59, 59);
        calendar.set(Calendar.MILLISECOND, 999);
        // in the following line, we'd rather call calendar.getTimeInMillis()
        // to avoid object creation, but that isn't supported in Java 1.3.1
        return calendar.getTime().getTime();
    }

    /**
     * Parses the string argument as a month.
     * <P>
     * This method is required to accept the format "YYYY-MM".  It will also
     * accept "MM-YYYY". Anything else, at the moment, is a bonus.
     *
     * @param s  the string to parse.
     *
     * @return <code>null</code> if the string is not parseable, the month 
     *         otherwise.
     */
    public static Month parseMonth(String s) {

        Month result = null;
        if (s != null) {

            // trim whitespace from either end of the string
            s = s.trim();

            int i = Month.findSeparator(s);
            if (i != -1) {
                String s1 = s.substring(0, i).trim();
                String s2 = s.substring(i + 1, s.length()).trim();

                Year year = Month.evaluateAsYear(s1);
                int month;
                if (year != null) {
                    month = SerialDate.stringToMonthCode(s2);
                    if (month == -1) {
                        throw new TimePeriodFormatException(
                            "Can't evaluate the month."
                        );
                    }
                    result = new Month(month, year);
                }
                else {
                    year = Month.evaluateAsYear(s2);
                    if (year != null) {
                        month = SerialDate.stringToMonthCode(s1);
                        if (month == -1) {
                            throw new TimePeriodFormatException(
                                "Can't evaluate the month."
                            );
                        }
                        result = new Month(month, year);
                    }
                    else {
                        throw new TimePeriodFormatException(
                            "Can't evaluate the year."
                        );
                    }
                }

            }
            else {
                throw new TimePeriodFormatException(
                    "Could not find separator."
                );
            }

        }
        return result;

    }

    /**
     * Finds the first occurrence of ' ', '-', ',' or '.'
     *
     * @param s  the string to parse.
     * 
     * @return <code>-1</code> if none of the characters where found, the
     *      position of the first occurence otherwise.
     */
    private static int findSeparator(String s) {

        int result = s.indexOf('-');
        if (result == -1) {
            result = s.indexOf(',');
        }
        if (result == -1) {
            result = s.indexOf(' ');
        }
        if (result == -1) {
            result = s.indexOf('.');
        }
        return result;
    }

    /**
     * Creates a year from a string, or returns null (format exceptions 
     * suppressed).
     *
     * @param s  the string to parse.
     *
     * @return <code>null</code> if the string is not parseable, the year 
     *         otherwise.
     */
    private static Year evaluateAsYear(String s) {

        Year result = null;
        try {
            result = Year.parseYear(s);
        }
        catch (TimePeriodFormatException e) {
            // suppress
        }
        return result;

    }

}