oglimmer/utils

package de.oglimmer.utils.date;

import java.util.Calendar;
import java.util.Date;

/**
 * Calculates a human readable representation of a date/time difference.
 * 
 * @author Oli Zimpasser
 *
 */
final public class DateHelper {

    private DateHelper() {
        // no code here
    }

    /**
     * Calculates a human readable date/time difference.
     * 
     * @param d1
     *            a starting date
     * @param d2
     *            an end date
     * @return a string which reads like x days, y hours, z minutes ...
     */
    public static String formatDateDifference(Date d1, Date d2) {
        long[] td = DateHelper.getTimeDifference(d1, d2);
        if (td[0] > 0) {
            return td[0] + " day(s), " + td[1] + " hour(s)";
        }
        if (td[1] > 0) {
            return td[1] + " hour(s), " + td[2] + " minute(s)";
        }
        if (td[2] > 0) {
            return td[2] + " minute(s), " + td[3] + " second(s)";
        }
        return td[3] + " second(s)";
    }

    /**
     * Calculates the date/time difference of two date object.
     * 
     * @param d1
     *            a starting date
     * @param d2
     *            an end date
     * @return an array where the 0th element has the number of days, the 1st element the number of hours, the 2nd
     *         element the number of minutes, the 3rd element the number of seconds, the 4th element the number of
     *         millis.
     */
    public static long[] getTimeDifference(Date d1, Date d2) {
        long[] result = new long[5];

        Calendar cal = Calendar.getInstance();
        cal.setTime(d1);
        long t1 = cal.getTimeInMillis();

        cal.setTime(d2);

        long diff = Math.abs(cal.getTimeInMillis() - t1);
        final int ONE_DAY = 1000 * 60 * 60 * 24;
        final int ONE_HOUR = ONE_DAY / 24;
        final int ONE_MINUTE = ONE_HOUR / 60;
        final int ONE_SECOND = ONE_MINUTE / 60;

        long d = diff / ONE_DAY;
        diff %= ONE_DAY;

        long h = diff / ONE_HOUR;
        diff %= ONE_HOUR;

        long m = diff / ONE_MINUTE;
        diff %= ONE_MINUTE;

        long s = diff / ONE_SECOND;
        long ms = diff % ONE_SECOND;
        result[0] = d;
        result[1] = h;
        result[2] = m;
        result[3] = s;
        result[4] = ms;

        return result;
    }
}