What class to use for date-related calculations.

[Anton Golovin]

I need to disregard records more than 48 hours removed. So what would you advise I use: Date or Calendar?

[mike acre]

Date is lighter & faster (by a huge amount) and simpler for Mr JP and there is no need for Calendar.

You can get a Date from the database format using SimpleDateFormat, then you can subtract 48hrs from it and compare it with the current date.

[peter wooster]

Originally posted by mike acre:
Date is lighter & faster (by a huge amount) and simpler for Mr JP and there is no need for Calendar.

You can get a Date from the database format using SimpleDateFormat, then you can subtract 48hrs from it and compare it with the current date.

Beware of the use of Date and attempts to determine today's date from it. The value is stored in UTC (GMT) and as such if you aren't in England or its summer, your value for midnight isn't the same as Date's. The easiest way around this is to use the SimpleDateFormat to convert midnight this morning to a Date and then use that in calculations.

[Anton Golovin]

Here's the method... I bet there is an easier way...

 
 /**
     * Checks if a room is bookable in relation to whatever operating parameters
     * figure into such a determination.
     *
     * @param room String[], the record to determine the bookability of.
     * @return boolean bookable or not.
     */
    public boolean isBookable(String[] room) {
        // stores room's availability date
        final String date = room[DATE_POSITION];
        // stores year, month, and day of room's availability as separate
        // entries
        String[] dateValues = date.split(DATE_SEPARATOR);
        // will store integer values of the same as above
        final int[] dateValuesAsInt = new int[dateValues.length];
 
        try { // populates integer array with integer-valued date components
            for (int i = 0; i < dateValuesAsInt.length; i++) {
                dateValuesAsInt[i] = Integer.parseInt(dateValues[i]);
                // System.out.println(dateValuesAsInt[i]);
            }
            // if something fails, room record contains corrupt date
            // and bookability is indeterminate, which is false for this
            // method's purposes
        } catch (NumberFormatException nfEx) {
            return false;
        }
 
        // stores the current date on the server machine
        final Date currentDate = new Date();
 
        // if year, month, and date match, room is bookable (it's today)
        if ((dateValuesAsInt[DATE_YEAR_POSITION] ==
            (currentDate.getYear() + 1900)) &
            (dateValuesAsInt[DATE_MONTH_POSITION] ==
            (currentDate.getMonth() + 1)) &
            (dateValuesAsInt[DATE_DAY_POSITION] == currentDate.getDate())) {
                // System.out.println("Today. ");
            return true;
        }
 
        // System.out.println("Current: " + currentDate.getTime());
        // figures out the availability date as a Date object
        final Date recordDate = new Date(dateValuesAsInt[DATE_YEAR_POSITION] -
                                         1900,
                                         dateValuesAsInt[DATE_MONTH_POSITION] -
                                         1,
                                         dateValuesAsInt[DATE_DAY_POSITION]);
        // System.out.println("Record: " + recordDate.getTime());
 
        // figures out if the room was available in the PAST
        // (code above matching year, month and day, accounts for some cases
        // where the code below would indicate a false, while the room
        // would be bookable, such as when current time is past midnight of day
        // n and room is bookable on day n, i.e., today)
        if ((recordDate.getTime() - currentDate.getTime()) <= 0) {
            // System.out.println("Negative time.");
            return false;
        }
        // figures out if the availability date falls within acceptable
        // operating parameters (i.e., within a certain number of hours)
        if ((recordDate.getTime() - currentDate.getTime()) >
            HOURS * 60 * 60 * 1000) {
           // System.out.println("Difference: " +
           //                    (recordDate.getTime() - currentDate.getTime()) /
            //                   3600);
            // System.out.println("Failed record at time calc.");
            return false;
        }
        // confirms bookability
        // System.out.println("Record is bookable.");
        return true;
    }
 

[ September 07, 2004: Message edited by: Anton Golovin ]

[peter wooster]

Originally posted by Anton Golovin:
Here's the method... I bet there is an easier way...

Here's what I do, I only allow today, tomorrow and the day after.

/**
 * determine if this record is available to be booked using the 48hr rule 
 */     
    public boolean isWithin48hrs() {
        Date minDate = new Date();
        try {
            minDate = Functions.parseDate(Functions.formatDate(minDate));
        } catch (java.text.ParseException e) {
            e.printStackTrace();
        }
        Date maxDate = new Date(minDate.getTime()[phone]L*2);
        System.out.println("mindate="+Functions.formatDate(minDate)+
            " maxdate="+Functions.formatDate(maxDate));
        return !(date.after(maxDate) || date.before(minDate));
    }

It calsulates minDate as midnight this morning, then calculates the max date as 2 days later. Since all values are at midnight, time == 0, this will work. Here's the Functions methods:

    private static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd"); // db date format
 
    public static Date parseDate(String date) throws ParseException {
        return dateFormat.parse(date);
    }
    public static String formatDate(Date date) {
        return dateFormat.format(date);
    }