《Java数据结构与算法》笔记-CH5-链表-9实现带迭代器的链表

/**
* 节点类
*/
class LinkNode {
private long data;
public LinkNode next;

public LinkNode(long d) {
this.data = d;
}

public String toString() {
return String.valueOf(this.data);
}
}

/**
* 带迭代器的链表
*/
class LinkListWithIterator {
private LinkNode first;//链表头结点

public LinkListWithIterator() {
first = null;
}

public LinkNode getFirst() {
return first;
}

public void setFirst(LinkNode ln) {
this.first = ln;
}

public boolean isEmpty() {
return first == null;
}
/**
* 得到迭代器
* @return
*/
public ListIterator getIter() {
return new ListIterator(this);
}

@Override
public String toString() {
if (isEmpty())
return "[]";
StringBuilder sb = new StringBuilder();
sb.append("[");
LinkNode current = first;
while (current != null) {
sb.append(current.toString()).append(",");
current = current.next;
}
sb.deleteCharAt(sb.length() - 1);
sb.append("]");
return sb.toString();
}
}
/**
* 迭代器
*/
class ListIterator {
private LinkListWithIterator ourList;
private LinkNode previous;
private LinkNode current;
/**
* 初始化时传入相应的链表
* @param list
*/
public ListIterator(LinkListWithIterator list) {
this.ourList = list;
reset();
}
/**
* 重置迭代器
*/
public void reset() {
current = ourList.getFirst();
previous = null;
}
/**
* 判断迭代器是否到了链表末尾
* @return
*/
public boolean atEnd() {
return current.next == null;
}
/**
* 迭代器指针向下移动
*/
public void nextLink() {
previous = current;
current = current.next;
}
/**
* 获取迭代器当前节点
* @return
*/
public LinkNode getCurrent() {
return current;
}
/**
* 从迭代器当前current处向后面插入新节点
* @param node
*/
public void insertAfter(LinkNode node) {
if (ourList.isEmpty()) {
ourList.setFirst(node);
current = node;
} else {
node.next = current.next;
current.next = node;
nextLink();
}
}
/**
* 从迭代器当前current处向前面插入新节点
* @param node
*/
public void insertBefore(LinkNode node) {
if (previous == null) {
node.next = ourList.getFirst();
ourList.setFirst(node);
reset();
} else {
node.next = previous.next;
previous.next = node;
current = node;
}
}
/**
* 删除迭代器当前节点
* @return
*/
public LinkNode deleteCurrent() {
LinkNode temp = current;
if (previous == null) {
ourList.setFirst(current.next);
reset();
} else {
previous.next = current.next;
if (atEnd())
reset();
else
current = current.next;
}
return temp;
}
}

public class IteratorDemo {
public static void main(String[] args) {
LinkListWithIterator list = new LinkListWithIterator();
ListIterator it = new ListIterator(list);
for (int i = 0; i < 6; i++) {
long rand = (long) (Math.random() * 100);
LinkNode node = new LinkNode(rand);
System.out.print("生成节点:" + node.toString() + ",");
if (i % 2 == 0) {
System.out.print("当前current为:" + it.getCurrent());
it.insertBefore(node);
System.out.println(",执行insertBefore:" + list.toString());
} else {
System.out.print("当前current为:" + it.getCurrent());
it.insertAfter(node);
System.out.println(",执行insertafter:" + list.toString());
}
}
System.out.println("list最终为:" + list.toString());
System.out.println("current节点为" + it.getCurrent() + ",删除节点" + it.deleteCurrent() + ",结果为:" + list.toString());
System.out.println("此时current为：" + it.getCurrent());
it.reset();
System.out.println("重置后current为：" + it.getCurrent());
while (!list.isEmpty()) {
System.out.println("删除current:" + it.deleteCurrent() + ",结果为:" + list.toString());
}
}
}