Question

JAVA

Have not gotten the public Iterator<Item> iterator() . Can someone explain it please?

import java.util.Iterator;

/*

* GroupsQueue class supporting addition and removal of items

* with respect to a given number of priorities and with

* respect to the FIFO (first-in first-out) order for items

* with the same priority.

*

* An example, where GroupsQueue would be useful is the airline

* boarding process: every passenger gets assigned a priority,

* usually a number, e.g., group 1, group 2, group 3, etc. and

* the passengers line up at the end of the queue of their groups

* in a FIFO fashion; and, when removing from the GroupsQueue,

* i.e., when the passengers are boarding the plane, they get

* removed first by their group priorities and then by their FIFO

* ordering within that particular priority group.

*

* Your homework is to implement the below GroupsQueue data

* structure, so that it functions in the way described above.

*

* You may use the provided Queue class for implementing the

* GroupsQueue class.

*/

public class GroupsQueue<Item> implements Iterable<Item> {

   private Node<Item> first;

      private Node<Item> last;

   private int n;

   private static class Node<Item> {

   private Item item;

   private Node<Item> next;

   }

  

   public void Queue() {

   first = null;

   last = null;

   n = 0;

   }

   // TODO : implement the data structure (20 points)

   /**

   * Initializes an empty GroupsQueue with g groups

   * @return

   */

   public GroupsQueue(int g) {

   first = new Node<>();

   last = first;

   for(int i=1; i<=19; i++){

   last.next = new Node<>();

last = last.next;

   }

   }

       // TODO : implement the constructor (20 points)

  

   /**

   * Is this GroupsQueue empty?

   */

   public boolean isEmpty() {

       return size() == 0;

   }

  

   /**

   * Returns the number of items in the GroupsQueue.

   */

   public int size() {

       return n; // TODO (20 points)

   }

  

   /**

   * Adds the item to this GroupsQueue with group id = gId.

   */

   public void add(Item item, int gId) {

       Node<Item> oldlast = last;

last = new Node<Item>();

last.item = item;

last.next = null;

if (isEmpty()) first = last;

else{

   oldlast.next = last;

}

n++;

}

       // TODO (20 points)

  

   /**

   * Removes and returns the item with the lowest group id

   */

   public Item remove() {

       return null;

} // TODO (20 points)

/**

* Returns an iterator that iterates over the items in this GroupsQueue

* in group id order (lowest id first) and in FIFO order in each group.

*/

   public Iterator<Item> iterator() {

      

       // TODO

       // BONUS (20 points)

       return null;

   }

}

Answer 1

import java.util.Iterator;

public class GroupsQueue<Item> implements Iterable<Item> {

   private Node<Item> first;

      private Node<Item> last;

   private int n;

   private static class Node<Item> {

   private Item item;

   private Node<Item> next;

   }

  

   public void Queue() {

   first = null;

   last = null;

   n = 0;

   }

   // TODO : implement the data structure (20 points)

   /**

   * Initializes an empty GroupsQueue with g groups

   * @return

   */

   public GroupsQueue(int g) {

   first = new Node<>();

   last = first;

   for(int i=1; i<=19; i++){

   last.next = new Node<>();

last = last.next;

   }

   }

       // TODO : implement the constructor (20 points)

  

   /**

   * Is this GroupsQueue empty?

   */

   public boolean isEmpty() {

       return size() == 0;

   }

  

   /**

   * Returns the number of items in the GroupsQueue.

   */

   public int size() {

       return n; // TODO (20 points)

   }

  

   /**

   * Adds the item to this GroupsQueue with group id = gId.

   */

   public void add(Item item, int gId) {

       Node<Item> oldlast = last;

last = new Node<Item>();

last.item = item;

last.next = null;

if (isEmpty()) first = last;

else{

   oldlast.next = last;

}

n++;

}

       // TODO (20 points)

  

   /**

   * Removes and returns the item with the lowest group id

   */

   public Item remove() {

       return null;

} // TODO (20 points)

/**

* Returns an iterator that iterates over the items in this GroupsQueue

* in group id order (lowest id first) and in FIFO order in each group.

*/

    public Iterator<Item> iterator() {

      

       // TODO

       // BONUS (20 points)

       return null;

   }