JAVA Have not gotten the public Iterator<Item> iterator() . Can someone explain
ID: 3794734 • Letter: J
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;
}
}
Explanation / Answer
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;
}
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