//Date3.java
// static members examples

public class Date3 {
    //**********  static variables ***************
    //** static variable ("class variable") is per class, not per object.
    //one for the entire class.  each object does not have its own copy.
    private static int numberDates=0;    
    //common example is an object counter variable. 
    //incremented in each constructor,  
    //private so only this class can directly access it.

    //**final is a constant.  can not be changed.  
    //conventional to be in all caps and _
    //accessed thru class name: Date3.VALID_START_YEAR
    //examples: Math.PI    Integer.MAX_VALUE
    public static final int VALID_START_YEAR=1584;  //pretend...

    //**if not static, is instance variable.  each object has own copy.
    //**********  instance variables ***************
    private int year;  
    private int month;
    private int day;

    //**********  constructors ***************
    public Date3() {
	month = 1;
	day = 1;
	year = 1970;
	numberDates++;   //***  OR:   Date3.numberDates++;
    }

    public Date3(int newMonth, int newDay, int newYear) {
	month = newMonth;
	day = newDay;
	year = newYear;
	numberDates++;   //***
    }

    public Date3( Date3 other) {
	month = other.month;
	day = other.day;
	year = other.year;
	numberDates++;   //***
    }

    public Date3( String date) {
	java.util.StringTokenizer st = new java.util.StringTokenizer(date,"/");

	month = Integer.parseInt(st.nextToken()); //extract next token
	day =   Integer.parseInt(st.nextToken());
	year =  Integer.parseInt(st.nextToken());
	numberDates++;   //***
    }

    //**********  accessor methods ***************
    public int getYear() {
	return year;
    }
    
    public int getMonth() {
	return month;
    }
    
    public int getDay() {
	return day;
    }
    
    public String toString() {
	return(month + "/" + day + "/" + year);
    }

    //** static method is per class.  each object does not have own copy.
    //can only access static variables because there are no instance variables
    //because there is no object.
    //accessed thru class name:  Date3.getNumberDates()
    public static int getNumberDates() {
	return numberDates;
    }

    //**********  mutator methods ***************
    public void increment() {
	day++;   //stub for the actual method to be written later...
    }

    //**another static method example 
    public static void clearNumberDates() {
	numberDates = 0;
    }


    //** static method can provide a service/utility.  not associated
    //with any object.  
    //Examples:  Math.sqrt  JOptionPane.showInputDialog  Integer.parseInt
    public static boolean isValidDay(int month, int day, int year) {
	//bunch of code will go here to determine if month day year 
	//combination is valid or not.
	return true;  //or false...
    }
}
/*
client code:
  if (myYear < Date3.VALID_START_YEAR)
      System.out.println("Years before "+Date3.VALID_START_YEAR+" are no good");

 //each Date3 object created increments the numberDates variable.
 //client can learn its value:
  System.out.println("Number of Date objects created:"+Date3.getNumberDates());

  //reset the application.  dispose of all date objects, then:
  Date3.clearNumberDates();

 //use the valid day combo checker:
  if (Date3.isValidDay(m,d,y))...
*/