//QueofDates.java
//enqueue and dequeue strings to/from a queue.
//the queue can be bounded or unbounded in size.

//LinkedList is used as the queue.
//Its addLast() is the enqueue operation
// (end of the LinkedList is the tail of the queue).
//Its removeFirst()is the dequeue operation
// (front of the LinkedList is the head of the queue).

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

public class QueofDates {

public static void main(String[] args) {
String input, userCommand, headOfQueue, newTailOfQueue;
char op;

int queueMaxSize=-1; //fakeout compiler
boolean isQueueBounded;

ArrayList myDatesList = new ArrayList();

LinkedList myQueue = new LinkedList(); //***create empty queue


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

//**array list of random Dates
for (int i=1; i<=queueMaxSize; i++) {
myDatesList.add(generateRandomDate()); //**pseudo data...
}

//iterate over them
Iterator it=myDatesList.iterator();
System.out.println();
System.out.println("Here are your dates: ");

Date thisDate;
while (it.hasNext()) {
//reference to the Date in the list.
//***next() returns Object, must cast to Date:
thisDate = (Date)(it.next());
//thisDate = (it.next()); //**failure to cast would be compile error
System.out.print(thisDate);
//***access a method of the Date object:
System.out.println(" Month is: " + thisDate.getMonth());
}
System.out.println();


//what does sorting do to Dates?
//Collections.sort(myDatesList); //***would be runtime error.
//***there is no "natural ordering" for user-defined classes.
//***must specify how dates are compared with a Comparator.
//DateComparator is defined in another file.
Collections.sort(myDatesList,new DateComparator()); //***

it = myDatesList.iterator();
System.out.println("Here are your dates in sorted order: ");

while (it.hasNext()) {

System.out.println(it.next());
    
//while (it.hasNext()) {
    //thisDate = (Date)(it.next());          
    //System.out.print(thisDate);
    //System.out.println("     Month is: " + thisDate.getMonth());

}
System.out.println();

printQueue( myQueue ); //show queue at every operation

while (it.hasNext()) {
    thisDate = (Date)(it.next());          
    System.out.print(thisDate);
    System.out.println("     Month is: " + thisDate.getMonth());
}
System.out.println();
                        
printQueue( myQueue ); //show queue at every operation

do {
    userCommand = JOptionPane.showInputDialog( "Enqueue or Dequeue or Quit" );
     op =  userCommand.toUpperCase().charAt(0);
    if (op == 'E') {
          
  if (myQueue.size()==queueMaxSize)  //***
      System.out.println("  Queue is full!  Can not enqueue.");
  else {
  
   it = myDatesList.iterator();
   thisDate = (Date)(it.next());
   myQueue.addLast(thisDate); //***** enqueue
    
  }
     }
     else if (op == 'D') {
  if (!myQueue.isEmpty()) {   //***** check queue (LinkedList) is not empty
      //***** dequeue Obect cast to needed type:
      //headOfQueue = (String) myQueue.removeFirst();
      thisDate = (Date)(it.next());
      //myQueue.removeFirst(thisDate);   //***** dequeue
      //it = myQueue.iterator();
      
   //System.out.println("Dequeued: " + headOfQueue);
    System.out.println("Dequeued: "); }
    
else
     System.out.println("  Queue is empty!  Nothing to dequeue.");
    }
   printQueue( myQueue );  //show queue at every operation


} while (op != 'Q');

System.exit(0);
}

static void printQueue( LinkedList q) {
System.out.print("Queue is: ");
//don't normally iterate over a queue. here for illustration purposes.
Iterator items = q.iterator();
while (items.hasNext())
System.out.print(items.next()+" ");
System.out.println();
}
//generate a random Date. Note this is not a method of the Date class.
//it creates and returns a Date object.
public static Date generateRandomDate() {
int year, month, day=0;

year = (int)(Math.random()*20+1995); // +/- 10 years from 2005
month = (int)(Math.random()*12+1);
switch (month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
day = (int)(Math.random()*31+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;
}
//instantiate a Date object using the 3-arg constructor,
//then return the object to caller.
return new Date(month,day,year);

}
}

public class Date implements Comparable<Date> {
...
...
   // must implement this method for Comparable<Date> interface
   public int compareTo( Date otherDate) {
   ...
   ...
   }
...
)