//DatesHashsetTest.java
//create random Dates and add to hash set.  
//Date and IncDate are in this file for a standalone demo program.
//How are duplicates determined?  Date must override equals() and hashCode()

import java.util.*;      
import javax.swing.*;

public class DatesHashSetTest {
    public static void main(String[] args) {
	String input;
	int size;
	
	HashSet myDatesHashSet = new HashSet();

	input = JOptionPane.showInputDialog( "Enter number of random dates" );
	size = Integer.parseInt( input );

	Date randDate;
	for (int i=1; i<=size; i++) {  
	    randDate = generateRandomDate();
	    System.out.print(randDate);
	    if (myDatesHashSet.add(randDate))
		System.out.println("   Added to set!");
	    else
		System.out.println("   Duplicate already in set. Not added to set!");
	}

	Iterator it = myDatesHashSet.iterator();
	System.out.println("Here are your unique random dates in the set: ");
	while (it.hasNext())
	    System.out.print(it.next() + " ");    
	System.out.println();


	System.exit(0);
    }
    
    //generate a random Date or IncDate.  
    //between m1/d1/y1 and m2/d2/y2
    //    public static Date generateRandomDate(int y1, int m1, int d1, int y2, int m2, int d2) {
    public static Date generateRandomDate() {
	int year, month, day=0;

	//	year = (int)(Math.random()*);  
	year = 2000;
    	//month = (int)(Math.random()*12+1);
	month = 1;
	switch (month) {
	case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12:
	    //day = (int)(Math.random()*31+1);
	    day = (int)(Math.random()*10+1);

	    break;
	case 4:
	case 6:
	case 9:
	case 11:
	    day = (int)(Math.random()*30+1);
	    break;
	case 2:
	    if (year%4==0 && year%100!=0 || year%400==0)  //leap year test
  	        day = (int)(Math.random()*29+1);
	    else
  	        day = (int)(Math.random()*28+1);
	    break;
	}    	
	//*** 50 50 whether it's Date or IncDate
	if (Math.random() < .5)
	    return new Date(month,day,year);
	else
	    return new IncDate(month,day,year);
    }
}

class Date     //same as in ch01.  ***added equals() and hashCode()
{
  protected int year;
  protected int month;
  protected int day;

  public Date(int newMonth, int newDay, int newYear)
  {
    month = newMonth;
    day = newDay;
    year = newYear;
   }

  public int yearIs()
  {
    return year;
  }

  public int monthIs()
  {
    return month;
  }

  public int dayIs()
  {
    return day;
  }

  public String toString()
  {
    return(month + "/" + day + "/" + year);
  }

    //***override equals() of Object.
    //***used to determine if two objects (of Date class) are "equal".
    //***MUST be overridden to use Date objects (uniquely, as keys) in a HashSet. 
    //***equality is defined by this method. 
    //***without this method, two objects are equal only if their references are the same.
    //***must be this signature:  parameter MUST be type Object.
    public boolean equals( Object other ) {   //parameter will be the other Date
	//***check that other really is Date, 
	//**then (safely) downcast to Date to access instance variables
	if ((other instanceof Date) && 
	    ((((Date)other).year==year) &&
	     (((Date)other).month==month) &&
	     (((Date)other).day==day)))
	    return true;
	else
	    return false;    //if other is null, or not a Date, or doesn't equal
    }

    //equals must be 
    //1. reflexive: x.equals(x) is true
    //2. symmetric: x.equals(y) == y.equals(x)
    //3. transitive: if x.equals(y) and y.equals(z) then x.equals(z)
    //also: x.equals(null) is false



    //***override hashcode() of Object
    //***if two Dates are equal, they must have same hashcode.
    //***must be this signature:
    public int hashCode() {
	//return 1492;  //works but inefficient   //?? how to make good hash??
	//some function of the instance variables modded by some prime
	return (year + month + day) % 101;  
    }
}


 class IncDate extends Date   //same as in ch01
{
  public IncDate(int newMonth, int newDay, int newYear)
  {
    super(newMonth, newDay, newYear);
   }

  public void increment()
  {
    // increment algorithm goes here
    // it updates the year, month, and day attributes
    day = day + 1;
  }
}