CalendarUtil

 package ch.makery.address.util;

 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;

 /**
  * Helper functions for handling dates.
  */
 public class CalendarUtil {

   /**
   * Default date format in the form 2013-03-18.
   */
   private static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd");

   /**
   * Returns the given date as a well formatted string. The above defined date
   * format is used.
   *
   * @param calendar date to be returned as a string
   * @return formatted string
   */
   public static String format(Calendar calendar) {
       if (calendar == null) {
           return null;
       }
       return DATE_FORMAT.format(calendar.getTime());
   }

   /**
   * Converts a String in the format "yyyy-MM-dd" to a Calendar object.
   *
   * Returns null if the String could not be converted.
   *
   * @param dateString the date as String
   * @return the calendar object or null if it could not be converted
   */
   public static Calendar parse(String dateString) {
       Calendar result = Calendar.getInstance();
       try {
           result.setTime(DATE_FORMAT.parse(dateString));
           return result;
       } catch (ParseException e) {
           return null;
       }
   }

   /**
   * Checks the String whether it is a valid date.
   *
   * @param dateString
   * @return true if the String is a valid date
   */
   public static boolean validString(String dateString) {
       try {
           DATE_FORMAT.parse(dateString);
           return true;
       } catch (ParseException e) {
           return false;
       }
   }
 }