[英]Circular linked list and iterator
我在讓迭代器實際工作並測試我的add和next方法方面遇到麻煩。 我想知道是否有人可以指出我所缺少的。 我花了一段時間,似乎無法弄清楚如何正確地初始化對象,一直說不能解析為一個類型。 謝謝,這是我的主要課程
public class CircularList<E> {
private int size = 0;
//Inner Class
private static class Node<E>{
private E data;
private Node<E> next=null;
private Node<E> previous=null;
private Node(E dataItem) {
data = dataItem;
}
}
//Iterator
public class CircleIter implements ListIterator<E>{
private Node<E> nextItem;
private Node<E> lastItemReturned;
private int index = 0;
public CircleIter(){
nextItem=null;
lastItemReturned=null;
}
@Override
public void add(E data) {
Node<E> newNode = new Node<E>(data);
if(index==0){
newNode.next=newNode;
newNode.previous=newNode;
nextItem=newNode;
lastItemReturned=newNode;
}
else{
newNode.previous=nextItem.previous;
nextItem.previous.next=newNode;
newNode.next=nextItem;
nextItem.previous=newNode;
}
index++;
size++;
}
@Override
public boolean hasNext() {
return nextItem != null;
}
@Override
public boolean hasPrevious() {
return (lastItemReturned.next == null && size != 0)
|| lastItemReturned.previous != null;
}
@Override //need to look over
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
lastItemReturned = nextItem;
nextItem = nextItem.next;
index++;
return lastItemReturned.data;
}
@Override
public int nextIndex() {
return index;
}
@Override //need to look over
public E previous() {
nextItem=lastItemReturned;
lastItemReturned=lastItemReturned.previous;
index--;
return nextItem.data;
}
@Override
public int previousIndex() {
return index-1;
}
//remove last item returned through next&previous method
@Override
public void remove() {
if (lastItemReturned == null) {
throw new IllegalStateException();
}
nextItem.previous=lastItemReturned.previous;
lastItemReturned.previous.next=nextItem;
index--;
size--;
lastItemReturned = nextItem.previous;
}
@Override
public void set(E node) {
if (lastItemReturned == null) {
throw new IllegalStateException();
}
lastItemReturned.data = node;
}
} //end of iterator class
}
我的考試班
import CircularList.CircleIter;
public class CircularListTest {
public static void main(String[] args) {
CircularList<Integer> intList = new CircularList<Integer>();
CircleIter<Integer> iter= intList.CircleIter<Integer>();
iter.add(5);
}
}
如果要創建CircularList.CircleIter
類的實例,則應使用運算符“ new”。
CircularList.CircleIter
是CircularList.CircleIter
類的內部類(非靜態嵌套類),因此,為了創建它的新實例,您應該使用特殊的語法提供封閉類的實例:
CircularList<Integer>.CircleIter iter = intList.new CircleIter();
通常,集合會公開用於創建迭代器的特殊方法(例如,List中的iterator()方法),以向使用者隱藏此語法。
正如Alex Sou先前提到的,在您的定義中僅參數化了封閉類。
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