CalendarDate

Die Klasse CalendarDate basiert auf den Algoritmen, die hier vorgestellt werden: http://alcor.concordia.ca/~gpkatch/gdate-algorithm.html .

Die weiter unten stehende Klasse CalendarDateDemo zeigt ein Anwendungsbeispiel.

<code=java> import java.util.Calendar;

public class CalendarDate {

   private long year;
   private long month;
   private long day;
   //Earliest date on Gregorian calendar:
   private static long calstart = days(new CalendarDate(1582, 10, 1));
   final static Calendar NOW = Calendar.getInstance();

   public CalendarDate() {
       this(NOW.get(Calendar.YEAR), NOW.get(Calendar.MONTH) + 1, NOW.get(Calendar.DAY_OF_MONTH));
   }

   public CalendarDate(final long year, final long month, final long day) {
       this.year = year;
       this.month = month;
       this.day = day;
   }

   /* convert day number to CalendarDate (year,month,day)*/
   public static CalendarDate toCalendarDate(final long dayNumber) {
       long year = (10000 * dayNumber + 14780) / 3652425;
       long day = dayNumber - (year * 365 + year / 4 - year / 100 + year / 400);
       if (day < 0) {
           year--;
           day = dayNumber - (year * 365 + year / 4 - year / 100 + year / 400);
       }
       long month = (52 + 100 * day) / 3060;
       return new CalendarDate(year + (month + 2) / 12,
               (month + 2) % 12 + 1,
               day - (month * 306 + 5) / 10 + 1);
   }

   /* return day number, or throw IllegalArgumentException if bad date */
   public static long days(final CalendarDate date) {
       long dayNumber = toDay(date);
       if (dayNumber < calstart) {
           throw new IllegalArgumentException("WARNING: Dates before Oct. 1582 are inaccurate.");
       }
       if (!date.equals(toCalendarDate(dayNumber))) {
           throw new IllegalArgumentException("Illegal date " + date);
       }
       return dayNumber;
   }

   /* convert date to day number */
   public static long toDay(final CalendarDate d) {
       long month = (d.getMonth() + 9) % 12; //mar=0, feb=11
       long year = d.getYear() - month / 10;   //if Jan/Feb, year--
       return year * 365 + year / 4 - year / 100 + year / 400
               + (month * 306 + 5) / 10 + (d.getDay() - 1);
   }

   @Override
   public String toString() {
       return getYear() + "." + getMonth() + "." + getDay();
   }

   public long getYear() {
       return year;
   }

   public long getMonth() {
       return month;
   }

   public long getDay() {
       return day;
   }

   public static long getCalstart() {
       return calstart;
   }

   @Override
   @SuppressWarnings("AccessingNonPublicFieldOfAnotherObject")
   public boolean equals(final Object obj) {
       if (obj == null) {
           return false;
       }
       if (getClass() != obj.getClass()) {
           return false;
       }
       final CalendarDate other = (CalendarDate) obj;
       if (this.year != other.year) {
           return false;
       }
       if (this.month != other.month) {
           return false;
       }
       if (this.day != other.day) {
           return false;
       }
       return true;
   }

   @Override
   public int hashCode() {
       int hash = 3;
       hash = 59 * hash + (int) (this.year ^ (this.year >>> 32));
       hash = 59 * hash + (int) (this.month ^ (this.month >>> 32));
       hash = 59 * hash + (int) (this.day ^ (this.day >>> 32));
       return hash;
   }

} </code=java> <code=java> import java.awt.*; import java.awt.event.*; import java.util.*; import javax.swing.*;

public class CalendarDateDemo {

   private CalendarDate dateResult;
   private String message;
   private long resultDays;
   public static final String USAGE = "Usage: y.m.d | y.m.d + n | y.m.d + y.m.d\n";

   public CalendarDateDemo(final String[] args) {
       if (args.length == 3 || args.length == 4 || args.length == 6) {
           message = "";
       } else {
           message = USAGE;//wrong number of arguments
       }
       long[] i = new long[args.length];
       /* Convert args to long integer */
       for (int j = 0; j < args.length; j++) {
           String string = args[j];
           try {
               i[j] = Long.parseLong(string);
           } catch (final NumberFormatException numberFormatException) {
               message += "Argument conversion error.\n";
           }

       }
       long base = 0;
       if (args.length > 3) { // arguments with base date
           try {
               base = CalendarDate.days(new CalendarDate(i[0], i[1], i[2]));
           } catch (IllegalArgumentException e) {
               message += e.getMessage() + "\n";
           }
       } else if (args.length == 3) {// no base date -> set current date as base:
           final Calendar NOW = Calendar.getInstance();
           CalendarDate date = new CalendarDate(NOW.get(Calendar.YEAR),
                   NOW.get(Calendar.MONTH) + 1, NOW.get(Calendar.DAY_OF_MONTH));
           base = CalendarDate.days(date);
       }
       //
       if ((args.length) % 3 == 1) { // Compute new date from offset
           CalendarDate date = CalendarDate.toCalendarDate(base + i[args.length - 1]);
           dateResult = date;
           resultDays = 0;
           if (base + i[args.length - 1] < CalendarDate.getCalstart()) {
               message += "WARNING: Dates before Oct. 1582 are inaccurate.\n";
           }
       } else if (args.length > 0 && args.length % 3 == 0) { // Compute days between dates
           CalendarDate date = new CalendarDate(i[args.length - 3],
                   i[args.length - 2], i[args.length - 1]);
           long days = 0;
           try {
               days = CalendarDate.days(date);
           } catch (IllegalArgumentException e) {
               message += e.getMessage() + "\n";
           }
           resultDays = days - base;
           dateResult = null;
       }
   }

   public CalendarDate getDateResult() {
       return dateResult;
   }

   public String getMessage() {
       return message;
   }

   public long getResultDays() {
       return resultDays;
   }

   private static void createAndShowGui() {
       final JFrame window = new JFrame(CalendarDateDemo.USAGE.replace("\n", ""));
       window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       window.setSize(400, 300);
       window.setLocationRelativeTo(null);
       final JTextField input1 = new JTextField(10);
       final JTextField input2 = new JTextField(10);
       final JLabel labelResult = new JLabel();
       final JTextArea labelMessage = new JTextArea();
       labelMessage.setEditable(false);
       labelMessage.setBackground(new Color(255, 255, 204));
       input1.setText(new CalendarDate().toString());
       input2.setText("2011.4.10");
       window.setLayout(new GridLayout(0, 1));
       window.add(input1);
       window.add(input2);
       window.add(labelResult);
       window.add(labelMessage);
       KeyListener listener = new KeyAdapter() {

           @Override
           public void keyReleased(final KeyEvent e) {
               String text1 = input1.getText();
               String text2 = input2.getText();
               String[] split = (text1 + "." + text2).split("\\.");
               CalendarDateDemo demo = new CalendarDateDemo(split);
               if (demo.getDateResult() != null) {
                   labelResult.setText(demo.getDateResult().toString());
               } else {
                   labelResult.setText(demo.getResultDays() + " days");
               }
               labelMessage.setText(demo.getMessage());
           }
       };
       input1.addKeyListener(listener);
       input2.addKeyListener(listener);
       window.setVisible(true);
       listener.keyReleased(null);
   }

   public static void main(final String... args) {
       Runnable gui = new Runnable() {

           public void run() {
               createAndShowGui();
           }
       };
       SwingUtilities.invokeLater(gui);
   }

} </code=java>