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package LinkedList;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
public class MyLinkedList<T> {
//*************************************************************
private DNode<T> header;
private int listSize;
//*************************************************************
public MyLinkedList() {
header = new DNode<T>();
listSize = 0;
}
//*************************************************************
private static class DNode<T> {
T nodeValue;
DNode<T> prev;
DNode<T> next;
public DNode() { // for header
nodeValue = null;
prev = this; // left
next = this; // right
}
public DNode(T item) {
nodeValue = item;
prev = this;
next = this;
}
}
//**************************************************************
public boolean isEmpty() {
return (header.prev == header || header.next == header);
}
public int size() {
return listSize;
}
//**************************************************************
private DNode<T> addBefore(DNode<T> curr, T item) {
DNode<T> newNode, prevNode;
newNode = new DNode<T>(item);
prevNode = curr.prev;
newNode.prev = prevNode;
newNode.next = curr;
prevNode.next = newNode;
curr.prev = newNode;
return newNode;
}
public boolean add(T item) {
addBefore(header, item);
listSize++;
return true;
}
public void addFirst(T item) {
addBefore(header.next, item);
listSize++;
}
public void addLast(T item) {
addBefore(header, item);
listSize++;
}
//**************************************************************
private void remove(DNode<T> curr) {
if(curr.next == curr) return;
DNode<T> prevNode = curr.prev, nextNode = curr.next;
prevNode.next = nextNode;
nextNode.prev= prevNode;
}
public boolean remove(Object o) {
for(DNode<T> p = header.next; p != header; p = p.next) {
if(o.equals(p.nodeValue)) {
remove(p);
listSize--;
return true;
}
}
return false;
}
//**************************************************************
public void printList() {
for(DNode<T> p = header.next; p != header; p = p.next)
System.out.println(p.nodeValue);
}
//**************************************************************
private class MyIterator implements Iterator<T> {
public DNode<T> nextNode = header.next;
public DNode<T> lastReturned = header;
public boolean hasNext() {
return nextNode != header;
}
public T next() {
if(nextNode == header)
throw new NoSuchElementException("");
lastReturned = nextNode;
nextNode = nextNode.next;
return lastReturned.nodeValue;
}
public void remove() {
if(lastReturned == header)
throw new IllegalStateException("");
MyLinkedList.this.remove(lastReturned);
lastReturned = header;
listSize--;
}
}
//**************************************************************
private class MyListIterator extends MyIterator implements ListIterator<T> {
private int nextIndex;
MyListIterator(int index) {
if(index < 0 || index > listSize)
throw new IndexOutOfBoundsException("");
//如果index小于listSize/2,就从表头开始查找定位,否则就从表尾开始查找定位
if(index < (listSize >> 1)) {
nextNode = header.next;
for(nextIndex = 0; nextIndex < index; nextIndex++)
nextNode = nextNode.next;
}else {
nextNode = header;
for(nextIndex = listSize; nextIndex > index; nextIndex--)
nextNode = nextNode.prev;
}
}
public boolean hasPrevious() {
return nextIndex != 0;
//return nextNode.prev != header;
}
public T previous() {
if (nextIndex == 0)
throw new NoSuchElementException("no");
lastReturned = nextNode = nextNode.prev;
nextIndex--;
return lastReturned.nodeValue;
}
public void remove() {
if(lastReturned == header)
throw new IllegalStateException("");
MyLinkedList.this.remove(lastReturned);
nextIndex--;
listSize--;
if(lastReturned == nextNode)
nextNode = nextNode.next;
lastReturned = header;
}
public void add(T item) {
MyLinkedList.this.addBefore(nextNode, item);
nextIndex++;
listSize++;
lastReturned = header;
}
public void set(T item) {
if (lastReturned == header)
throw new IllegalStateException();
lastReturned.nodeValue = item;
}
public int nextIndex() {
return nextIndex;
}
public int previousIndex() {
return nextIndex - 1;
}
}
//**************************************************************
public Iterator<T> iterator() {
return new MyIterator();
}
//**************************************************************
public ListIterator<T> listIterator(int index) {
return new MyListIterator(index);
}
//**************************************************************
public static void main(String[] args) {
MyLinkedList<String> t = new MyLinkedList<String>();
t.add("A");
t.add("B");
t.add("C");
t.add("D");
//t.remove("B");
//t.addFirst("AA");
//t.addLast("BB");
//t.printList();
/*
Iterator<String> it = t.iterator();
while(it.hasNext()) System.out.println(it.next()); // A B C D
*/
ListIterator<String> it = t.listIterator(t.size());
while(it.hasPrevious()) {
System.out.println(it.previous()); // D C B A
}
}
}// MyLinkedList end~