utils.java

The program is used for the calculations of the day , week , month on the calendar .

package us.k5n.ical;

import java.util.Calendar;
import java.io.*;


/**
  * iCal Utility class
  * @version $Id$
  * @author Craig Knudsen, [e-mail]
  */
class Utils
  implements Constants
{

  static public String getFileContents ( File f )
    throws IOException, FileNotFoundException
  {
    StringBuffer ret = new StringBuffer();
    BufferedReader input = null;
    input = new BufferedReader ( new FileReader ( f ) );
    String line = null;
    while ( ( line = input.readLine()) != null ) {
      ret.append ( line );
      ret.append ( CRLF );
    }
    if ( input!= null) {
      input.close();
    }
    return ret.toString();
  }

  /**
    * Convert a java.util.Calendar object to a YYYYMMDD String.
    * @param inDate	Date to convert
    * @return	The Date as a String in YYYYMMDD format
    */
  public static String CalendarToYYYYMMDD ( Calendar inDate )
  {
    StringBuffer ret = new StringBuffer ( 8 );
    ret.append ( inDate.get ( Calendar.YEAR ) );
    if ( inDate.get ( Calendar.MONTH ) + 1 < 10 )
      ret.append ( '0' );
    ret.append ( ( inDate.get ( Calendar.MONTH ) + 1 ) );
    if ( inDate.get ( Calendar.DAY_OF_MONTH ) < 10 )
      ret.append ( '0' );
    ret.append ( inDate.get ( Calendar.DAY_OF_MONTH ) );
    return ret.toString();
  }

  /**
    * Convert a YYYYMMDD String into a java.util.Calendar object.
    * Possible formats include: <ul>
    *  <li>  20001231 (date only, no time) </li>
    *  <li>  20001231T235900 (date with local time) </li>
    *  <li>  20001231T235900Z (date with utc time) </li>
    * </ul>
    * @param inDate	Date to convert
    * @return	The Date as a Calendar
    */
  public static Calendar YYYYMMDDToCalendar ( String inDate )
    throws BogusDataException, ParseException
  {
    Calendar ret = Calendar.getInstance ();
    if ( inDate.length() < 8 )
      throw new BogusDataException ( "Invalid date format '" + inDate + "'",
        inDate );
    int year = Integer.parseInt ( inDate.substring ( 0, 4 ) );
    int month = Integer.parseInt ( inDate.substring ( 4, 6 ) );
    int day = Integer.parseInt ( inDate.substring ( 6, 8 ) );
    // TODO: validate for each month and leap years, too
    // TODO: can java.util.Calendar handle dates before 1970 and after 2038?
    if ( day < 1 || day > 31 || month < 1 || month > 12 )
      throw new BogusDataException ( "Invalid date '" + inDate + "'", inDate );
    // TODO: parse time, handle localtime, handle timezone
    if ( inDate.length() > 8 ) {
      if ( inDate.charAt ( 8 ) == 'T' ) {
        try {
          int hour = Integer.parseInt ( inDate.substring ( 9, 11 ) );
          int minute = Integer.parseInt ( inDate.substring ( 11, 13 ) );
          int second = Integer.parseInt ( inDate.substring ( 13, 15 ) );
          ret.set ( year, month, day, hour, minute, second );
        } catch ( NumberFormatException nef ) {
          throw new BogusDataException ( "Invalid time in date string '" +
            inDate + "' - " + nef, inDate );
        }
      } else {
        // Invalid format
        throw new ParseException ( "Invalid date format '" + inDate + "'",
          inDate );
      }
    } else {
      // Just date, no time
      ret.set ( year, month, day );
    }
    return ret;
  }


  /**
    * Get the date for the first day of the week for the specified date.
    */
  public static Calendar startOfWeek ( Calendar cal, boolean sundayStartsWeek )
  {
     int dow = sundayStartsWeek ? Calendar.SUNDAY : Calendar.MONDAY;
     Calendar ret = (Calendar)cal.clone ();
     while ( ret.get ( Calendar.DAY_OF_WEEK ) != dow ) {
       ret.add ( Calendar.DATE, -1 );
     }
     return ret;
  }

  /**
    * Get the date for the first day of the week for the specified date.
    */
  public static Calendar endOfWeek ( Calendar cal, boolean sundayStartsWeek )
  {
     int dow = sundayStartsWeek ? Calendar.SATURDAY : Calendar.SUNDAY;
     Calendar ret = (Calendar)cal.clone ();
     while ( ret.get ( Calendar.DAY_OF_WEEK ) != dow ) {
       ret.add ( Calendar.DATE, 1 );
     }
     return ret;
  }


}