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Working with Date and Time

 
import java.util.*;
import java.text.*;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
 *This class has all method to be used by Timesheet throught the date and time related operations
 * @author Hemraj
 */
public class DateTime {

    /**
     * Change the date represented by Date object into the date format that is accepted by MS SQL Server 
     * @param d
     * @return
     */
    public String dateTime(Date d) {
        Calendar c = new java.util.GregorianCalendar();
        c.setTime(d);
        int yy = c.get(Calendar.YEAR);
        int mm = c.get(Calendar.MONTH) + 1;
        int dd = c.get(Calendar.DATE);
        int m = c.get(Calendar.MINUTE);
        int s = c.get(Calendar.SECOND);
        int hour = c.get(Calendar.HOUR_OF_DAY);
        String timeStamp = yy + "-" + mm + "-" + dd + " " + hour + ":" + m + ":" + s;
        return timeStamp;
    }

    /**
     * Covert the indian like 12/3/3009 date format into database date fromat lilke yyyy-mm-dd 
     * @param d
     * @return
     */
    public String dateFormat(String d) {
        int i1 = d.indexOf("/");
        int i2 = d.indexOf("/", i1 + 1);
        String dd = d.substring(0, i1).trim();
        String mm = d.substring(i1 + 1, i2).trim();
        String yy = d.substring(i2 + 1).trim();
        return yy + "-" + mm + "-" + dd;
    }

    /**
     * change date like 2008-01-14 15:53:06.000 into 14/1/2008
     * @param d
     * @return
     */
    public String formatDate(String d) {
        //d=d.substring(0,d.indexOf(" "));
        int i = d.indexOf("-");
        String yyyy = d.substring(0, i);
        int j = d.indexOf("-", i + 1);
        String mm = d.substring(i + 1, j);
        String dd = d.substring(j + 1, j + 1 + 2);
        return dd + "/" + mm + "/" + yyyy;
    }

    /**
     * Change the database date format into dd/mm/yyyy format
     * @param d
     * @return
     */
    public static String dbToIn(String d) {
        d = d.substring(0, d.indexOf(" "));
        int i = d.indexOf("-");
        String yyyy = d.substring(0, i);
        int j = d.indexOf("-", i + 1);
        String mm = d.substring(i + 1, j);
        String dd = d.substring(j + 1);
        return dd + "/" + mm + "/" + yyyy;
    }

    /**
     * Change the date format of Date object into indian format(dd/mm/yyyy); 
     * @param date
     * @return
     */
    public String formatDate(java.util.Date date) {
        Calendar c = new java.util.GregorianCalendar();
        c.setTime(date);
        int yy = c.get(Calendar.YEAR);
        int mm = c.get(Calendar.MONTH) + 1;
        int dd = c.get(Calendar.DATE);
        String timeStamp = dd + "/" + mm + "/" + yy;
        return timeStamp;

    }

    public String getDayName(int i) {
        String days[] = {"Mo", "Tu", "We", "Th", "Fr", "Sa", "Su"};
        return days[i - 1];
    }

    /**
     * Method to convert string like dd/mm/yyyy into Date object. 
     * E.g 12/02/2004 will be passed as argument at method gives you Date object
     * that contain the above date.
     * @param d
     * @return Date returns the Date object
     */
    public java.util.Date dateObject(String d) throws ParseException {
        int i1 = d.indexOf("/");
        int i2 = d.indexOf("/", i1 + 1);
        String dd = d.substring(0, i1).trim();
        String mm = d.substring(i1 + 1, i2).trim();
        String yy = d.substring(i2 + 1).trim();
        //return yy+"-"+mm+"-"+dd;
        Calendar c = new java.util.GregorianCalendar(Integer.parseInt(yy), Integer.parseInt(mm) - 1, Integer.parseInt(dd));
        return c.getTime();
    }

    /**
     * @author Hemraj
     * Calculate the difference between two dates represented by 2 java.util.Date object
     * @param first First Date object to be subtracted
     * @param second second date object from which fisrt date object to be subtracted
     * @return long value. Number of days
     */
    public long dateDiffInDays(java.util.Date first, java.util.Date second) {
        Calendar cFirst = new java.util.GregorianCalendar();
        cFirst.setTime(first);
        Calendar cSecond = new java.util.GregorianCalendar();
        cSecond.setTime(second);

        long milliseconds1 = cFirst.getTimeInMillis();
        long milliseconds2 = cSecond.getTimeInMillis();
        long diff = milliseconds2 - milliseconds1;
        //long diffSeconds = diff / 1000;
        //long diffMinutes = diff / (60 * 1000);
        //long diffHours = diff / (60 * 60 * 1000);
        long diffDays = diff / (24 * 60 * 60 * 1000);
        return diffDays;

    }

    /**
     * 
     * @param first
     * @param second
     * @return
     */
    public int campareDates(java.util.Date first, java.util.Date second) {
//        Calendar cFirst = new java.util.GregorianCalendar();
//        cFirst.setTime(first);
        return first.compareTo(second);

    }

    /**
     * Method to convert string like dd/mm/yyyy into Date object. 
     * E.g 12/02/2004 will be passed as argument at method gives you Date object
     * that contain the above date.
     * @param  d java.sql.Date object from resultset
     * @return Date returns the Date object
     */
    public java.util.Date dateObject(java.sql.Date d) {
        return (java.util.Date) d;
    }

    /**
     * get the next date from specified date for specified number of days
     * @param cd
     * @param days
     * @return
     */
    public java.util.Date nextDate(java.util.Date cd, int days) {
        Calendar c = new java.util.GregorianCalendar();
        c.setTime(cd);
        c.add(Calendar.DAY_OF_MONTH, days);
        return c.getTime();
    }

    /**
     * get previous date from specified date for specified number of days.
     * @param cd
     * @param days
     * @return
     */
    public java.util.Date previousDate(java.util.Date cd, int days) {
        Calendar c = new java.util.GregorianCalendar();
        c.setTime(cd);
        c.add(Calendar.DAY_OF_MONTH, -days);
        return c.getTime();
    }

    /**
     * get the name of day of date like dd/mm/yyyy
     * @param d
     * @return
     */
    public String getDayName(String d) throws Exception {
        java.util.Date date = dateObject(d);
        Calendar c = new java.util.GregorianCalendar();
        c.setTime(date);
        return getDayName(date);
    }

    /**
     * Get name of the day represented by specified date object
     * @param d
     * @return
     */
    public String getDayName(Date d) {
        DateFormat f = new SimpleDateFormat("EEEE");
        try {
            return f.format(d);
        } catch (Exception e) {
            e.printStackTrace();
            return "";
        }
    }
    public String getDaysName(int day,int month)
    {
         Calendar c1 = Calendar.getInstance();
         Calendar c2 = Calendar.getInstance(); // new GregorianCalendar();
         c2.setTime(new Date());
         int year = c2.get(Calendar.YEAR);
         c1.set(year, month, day);
         String name=getDayName(c1.getTime());
         return name.substring(0,2);
    }
    public static int daysInMonth(int month) {

        System.out.println("4. No of Days in a month for a given date\n");
        Calendar c1 = Calendar.getInstance(); // new GregorianCalendar();
        //c1.setTime(cd);
        Calendar c2 = Calendar.getInstance(); // new GregorianCalendar();
        c2.setTime(new Date());
        int year = c2.get(Calendar.YEAR);
        //int month = c1.get(Calendar.MONTH);
        c1.set(year, month, 1);
        // int days = c1.get(Calendar.DATE);
        int[] daysInMonths = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        daysInMonths[1] += isLeapYear(year) ? 1 : 0;
        System.out.println("Days in " + month + "th month for year" + year + "is " + daysInMonths[c1.get(Calendar.MONTH)]);
        System.out.println();
        System.out.println("-------------------------------------");
        return daysInMonths[c1.get(Calendar.MONTH)];
    }

    public static boolean isLeapYear(int year) {

        if ((year % 100 != 0) || (year % 400 == 0)) {
            return true;
        }
        return false;
    }

    public static void main(String ar[]) throws Exception {
        //System.out.println(new DateTime().getDayName("13/4/2008"));
        //System.out.println(new DateTime().getDayName(new Date()));
        //System.out.println("Days = "+daysInMonth(7));
        int days=daysInMonth(3);
        for(int i=1;i<=days;i++)
        {
            System.out.println(i+"="+new DateTime().getDaysName(i, 3));
        }
    }
}

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