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Deque.java
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Deque.java
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import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* Created with IntelliJ IDEA.
* User: rshen
* Date: 7/14/14
* Time: 8:09 PM
* To change this template use File | Settings | File Templates.
*/
public class Deque<Item> implements Iterable<Item> {
private Node first;
private Node last;
private int count;
private class Node {
private Item item;
private Node next;
private Node prev;
public void setItem(Item value) { item = value; }
public Item getItem() {
return item;
}
public void setNext(Node value) { next = value; }
public Node getNext() {
return next;
}
public void setPrev(Node value) { prev = value; }
public Node getPrev() {
return prev;
}
}
public Deque() {
first = null;
last = first;
count = 0;
}
public boolean isEmpty() {
return first == null;
}
public int size() {
return count;
}
public void addFirst(Item item) {
if (item == null) {
throw new NullPointerException();
}
if (isEmpty()) {
first = new Node();
first.setItem(item);
first.setPrev(null);
first.setNext(last);
last = first;
} else {
Node newItem = new Node();
newItem.setItem(item);
newItem.setNext(first);
first.setPrev(newItem);
newItem.setPrev(null);
first = newItem;
}
count++;
}
public void addLast(Item item) {
if (item == null) {
throw new NullPointerException();
}
if (isEmpty()) {
last = new Node();
last.setItem(item);
last.setPrev(first);
last.setNext(null);
first = last;
} else {
Node newItem = new Node();
newItem.setItem(item);
newItem.setPrev(last);
last.setNext(newItem);
newItem.setNext(null);
last = newItem;
}
count++;
}
public Item removeFirst() {
if (isEmpty()) {
throw new NoSuchElementException();
}
Node removedNode = first;
first = first.getNext();
if (first != null) {
first.setPrev(null);
} else {
last = null;
}
removedNode.setNext(null);
count--;
return removedNode.getItem();
}
public Item removeLast() {
if (isEmpty()) {
throw new NoSuchElementException();
}
Node removedNode = last;
last = last.getPrev();
if (last != null) {
last.setNext(null);
} else {
first = null;
}
removedNode.setPrev(null);
count--;
return removedNode.getItem();
}
@Override
public Iterator<Item> iterator() {
return new DequeIterator();
}
private class DequeIterator implements Iterator<Item> {
private Node current = first;
@Override
public boolean hasNext() {
return current != null;
}
@Override
public Item next() {
if (current == null || current.getItem() == null) {
throw new NoSuchElementException();
}
Item returnItem = current.getItem();
current = current.getNext();
return returnItem;
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}
public static void main(String[] args) {
// Deque<Integer> test = new Deque<Integer>();
// System.out.println(test.size());
// System.out.println(test.isEmpty());
//
// test.addFirst(3);
//
// System.out.println(test.removeFirst());
//
// test.addLast(5);
//
// System.out.println(test.removeFirst());
//
// test.addFirst(2);
// test.addLast(4);
// System.out.println(test.size());
// System.out.println(test.isEmpty());
//
// test.addFirst(2);
// System.out.println(test.removeLast());
//
// test.addFirst(5);
// System.out.println(test.removeLast());
//
// test.addFirst(1);
// test.addFirst(2);
// test.addFirst(3);
// test.addFirst(4);
// System.out.println(test.removeLast());
// System.out.println(test.removeLast());
// System.out.println(test.removeLast());
// test.addFirst(5);
// System.out.println(test.removeLast());
// System.out.println(test.removeLast());
// System.out.println(test.isEmpty());
//
// test.addFirst(1);
//
// test.addLast(5);
//
// System.out.println(test.removeFirst());
// System.out.println(test.removeLast());
//
// System.out.println(test.size());
//
// Iterator dequeIterator = test.iterator();
// while (dequeIterator.hasNext()) {
// System.out.println(dequeIterator.next());
// }
}
}