import java.beans.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;

public class DateGUI extends Panel implements ItemListener {

// static constants
protected final static int FIRST_YEAR = 1980;
protected final static int  LAST_YEAR = 2005;

protected final static int DAYS_IN_FEBRUARY = 28;
protected final static int DAYS_IN_LEAP_FEB = 29;

protected final static String[] monthNames = {
	"January", "February", "March", "April", "May", "June",
	"July", "August", "September", "October", "November", "December"};

protected final static int[] numDays = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

// instance fields
protected GregorianCalendar calendar;

// GUI variables
protected Choice dayChoice, monthChoice, yearChoice;
protected int lastMaxDay = -1;

// PropertyChange helper object
protected PropertyChangeSupport butler;

//-------------------------------------------------------------------
// DateGUI Constructor
//-------------------------------------------------------------------
public DateGUI() {

	butler = new PropertyChangeSupport(this);

	// our date editor is internally reflected by a Calendar/Time object
	calendar = new GregorianCalendar();
	calendar.setTime(new Date());			// default "date" prop equals "now"

	// create the day, month, year choices and register for select events
	dayChoice	= buildDayChoice();		  dayChoice.addItemListener(this);
	monthChoice	= buildMonthChoice();	monthChoice.addItemListener(this);
	yearChoice	= buildYearChoice();	 yearChoice.addItemListener(this);

	// arrange the Choices next to each other using default LayoutManager
	add(monthChoice);
	add(dayChoice);
	add(yearChoice);

	// to polish GUI, we select Choice items to reflect current date
	reflectNewDate();
}
//-------------------------------------------------------------------
// set()/get() for 'Date' property
//-------------------------------------------------------------------
public void setDate(Date value) {
Date prevDate = getDate();

	calendar.setTime(value);
	reflectNewDate();
	butler.firePropertyChange("date", prevDate, getDate());
}
public Date getDate() {
	return calendar.getTime();
}
//-------------------------------------------------------------------
// Choice builders
//-------------------------------------------------------------------
protected Choice buildDayChoice() {
Choice days;

	days = buildChoiceFromRange(1, 31);	// default month day range
	days.setSize(20,16);
	return days;			// needs to be filled according to month
}
//-------------------------------------------------------------------
protected Choice buildMonthChoice() {
Choice months;

	months = buildChoiceFromStringList(monthNames);
	months.setSize(80,16);
	return months;
}
//-------------------------------------------------------------------
protected Choice buildYearChoice() {
Choice years;

	years = buildChoiceFromRange(FIRST_YEAR, LAST_YEAR);
	years.setSize(60,16);
	return years;
}
//-------------------------------------------------------------------
// Ensure that the days Choice only shows maxDay days (i.e. 28, 30, 31)
//-------------------------------------------------------------------
protected void setDaysChoiceLastDay(int maxDay) {

	// avoid expensive Choice massaging if possible
	if ( maxDay != lastMaxDay ) {
		String[] list = buildStringListFromRange(1, maxDay);
		setChoiceList(dayChoice, list);

		lastMaxDay = maxDay;
	}
}
//-------------------------------------------------------------------
// Utility function to create a Choice of integers [first..last]
//-------------------------------------------------------------------
public static Choice buildChoiceFromRange(int first, int last) {
String[] listOfIntegers;

	listOfIntegers = buildStringListFromRange(first, last);
	return buildChoiceFromStringList(listOfIntegers);
}
//-------------------------------------------------------------------
// Utility function to create a Choice from a list of Strings
//-------------------------------------------------------------------
public static Choice buildChoiceFromStringList(String[] list) {
Choice choice = new Choice();

	setChoiceList(choice, list);
	return choice;
}
//-------------------------------------------------------------------
// Utility function to create an array of Strings containing a range
// of integer values
//-------------------------------------------------------------------
public static String[] buildStringListFromRange(int first, int last) {
String[] list = new String[last - first + 1];

	for (int i=first; i <= last; i++) {
		list[i-first] = String.valueOf(i);
	}
	return list;
}
//-------------------------------------------------------------------
// Utility function to set the list of Choice items from a String[]
//-------------------------------------------------------------------
public static void setChoiceList(Choice choice, String[] list) {

	choice.removeAll();
	for (int i=0; i < list.length; i++) {
		choice.add(list[i]);
	}
}
//-------------------------------------------------------------------
// Select Choice items to reflect date property
//-------------------------------------------------------------------
protected void reflectNewDate() {
int currentDay,currentMonth,currentYear;

	currentDay   = calendar.get(calendar.DAY_OF_MONTH);	// 1-based
	currentMonth = calendar.get(Calendar.MONTH);		// 0-based
	currentYear  = calendar.get(Calendar.YEAR);

	// handle feb and leap years
	setDaysChoice(currentYear, currentMonth);

	  dayChoice.select(currentDay -1 );
	monthChoice.select(currentMonth);
	 yearChoice.select(currentYear -FIRST_YEAR);
}
//-------------------------------------------------------------------
// Modify days Choice component so that it lists the correct number of
// days for this year and month.
//-------------------------------------------------------------------
protected void setDaysChoice(int currentYear, int currentMonth) {

	if ( currentMonth == Calendar.FEBRUARY) {
		if (calendar.isLeapYear(currentYear)) {
			setDaysChoiceLastDay(DAYS_IN_LEAP_FEB);
		} else {
			setDaysChoiceLastDay(DAYS_IN_FEBRUARY);
		}
	} else {
		setDaysChoiceLastDay( numDays[currentMonth] );
	}
}
//-------------------------------------------------------------------
// Preferred size settings so we don't get squashed
//-------------------------------------------------------------------
public Dimension preferredSize() {		// 1.0-style
	return new Dimension(200,40);
}
public Dimension getPreferredSize() {	// 1.1-style
	return preferredSize();
}
//-------------------------------------------------------------------
// The ItemListener interface method
//-------------------------------------------------------------------
public void itemStateChanged(ItemEvent itemEvent) {
Choice choice;
int day, month, year;
int maxDaysForMonth;

	// find out which Choice fired the item selection event
	choice = (Choice) itemEvent.getSource();

	// note the new state of each Choice selection
	year	=  yearChoice.getSelectedIndex() + FIRST_YEAR;
	month	= monthChoice.getSelectedIndex();
	day		=   dayChoice.getSelectedIndex();	// 0..n-1

	// if user selected a new month or a new year,
	// update the days Choice to reflect the correct max # of days for month
	if ( choice == monthChoice || choice == yearChoice) {

		// set correct # of days for month (incl feb & leap years)
		setDaysChoice(year, month);

		// re-select old day if possible, otherwise last day of month
		maxDaysForMonth = dayChoice.getItemCount();
		day = Math.min(day, maxDaysForMonth-1 );
		dayChoice.select(day);
	}

	// Now that we've taken care of Feb and other classic calendar details
	// change our date property to reflect GUI and issue PropertyChangeEvent

	Date prevDate = getDate();

	day = dayChoice.getSelectedIndex() + 1;	// year and month already set
	calendar.set(year, month, day);

	butler.firePropertyChange("date", prevDate, getDate());
}
//-------------------------------------------------------------------
// PropertyChange Listeners management
//-------------------------------------------------------------------
public void addPropertyChangeListener(PropertyChangeListener listener) {
	 butler.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
	 butler.removePropertyChangeListener(listener);
}
//-------------------------------------------------------------------
// Self-test code
//-------------------------------------------------------------------
public static void main (String[] args) {
Frame window;
DateGUI dateEditor;

	window		= new Frame("Date editor tester");
	dateEditor	= new DateGUI();

	window.add("Center", dateEditor);
	window.setSize(new Dimension(210,70));
	window.setVisible(true);
}
} // End of Class DateGUI