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Deque.java
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Deque.java
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import java.util.Iterator;
public class Deque<Item> implements Iterable<Item> {
private Node front;
private Node rear;
private int size;
public Deque() {
this.front = null;
this.rear = null;
this.size = 0;
}
private class Node {
Item item;
Node next;
Node previous;
}
public boolean isEmpty() {
return (this.size == 0);
}
public int size()
{
return size;
}
public void addFirst(Item item) {
if (item == null) {
throw new java.lang.NullPointerException();
}
Node newNode = new Node();
newNode.item = item;
newNode.next = this.front;
newNode.previous = null;
if (!isEmpty())
this.front.previous = newNode;
else
this.rear = newNode;
this.front = newNode;
size++;
}
public void addLast(Item item) {
if (item == null) {
throw new java.lang.NullPointerException();
}
Node newNode = new Node();
newNode.item = item;
newNode.next = null;
newNode.previous = this.rear;
if (!isEmpty()) {
this.rear.next = newNode;
} else {
this.front = newNode;
}
this.rear = newNode;
size++;
}
public Item removeFirst() {
if (isEmpty()) {
throw new java.util.NoSuchElementException();
}
Item firstItem = this.front.item;
if (front.next != null) {
this.front.next.previous = null;
}
this.front = this.front.next;
size--;
if (isEmpty()) {
this.rear = null;
}
return firstItem;
}
public Item removeLast() {
if (isEmpty()) {
throw new java.util.NoSuchElementException();
}
Item lastItem = this.rear.item;
if (this.rear.previous != null)
this.rear.previous.next = null;
this.rear = rear.previous;
size--;
if (isEmpty()) {
this.front = null;
}
return lastItem;
}
public Iterator<Item> iterator() {
return new DequeIterator();
}
private class DequeIterator implements Iterator<Item> {
private Node current = front;
public boolean hasNext() {
return current != null;
}
public void remove() {
throw new java.lang.UnsupportedOperationException();
}
public Item next() {
if (!hasNext()) {
throw new java.util.NoSuchElementException();
}
Item item = current.item;
current = current.next;
return item;
}
}
public static void main(String args[]) {
Deque<Integer> d = new Deque<Integer>();
Iterator<Integer> a = d.iterator();
while (a.hasNext()) {
StdOut.println(a.next());
}
for (int i = 0; i < 10; i++) {
d.addFirst(i);
}
for (int i = 0; i < 10; i++) {
StdOut.println(d.removeFirst());
}
}
}