这是我在这里的第一篇文章！ 我是CS学生，所以我还在学习。如果您有任何建议或指针（哈哈..！）可以为我的代码结构或一般实践提供指导，我将不胜感激！
我被分配了一个使用循环链表在Java（https://docs.oracle.com/javase/7/docs/api/java/util/Queue.html）中重新实现Queue类的任务。我的意见书附在这个问题上。我在作业中收到的分数为零-根据评分者，我对链表的实现不是循环的。
我不想表现得过于自负或过于自信，因为我显然不知道自己在某种程度上在做什么，但是在155至161行中，我注释掉了打印出列表中下一个链接的数据。据我所知，列表中的节点是循环链接的，因为即使在打印完最后一个节点的数据之后，它们仍会继续打印第一个节点的数据。
例如（，而且我知道此段看起来很乱，我仅为调试目的将其设置为这样-实际上这是我已注释掉我的实际代码的部分）：
System.out.println("next: " + cursor.getNext().getData());
System.out.println("next.next: " + cursor.getNext().getNext().getData());
System.out.println("next.next.next: " + cursor.getNext().getNext().getNext().getData());
System.out.println("next.next.next.next: " + cursor.getNext().getNext().getNext().getNext().getData());
打印：
下一个：45
next.next：71
next.next.next：3
next.next.next.next：45
当三个节点包含列表中输入的数据时。
此外，从第30行开始的 add 方法将列表尾部之后的下一个节点分配给头部（而不是空值），因此列表应该循环循环，对吗？ 这是一段：
Node<T> node = new Node<T>(element);
if(isEmpty() == true){
head = node;
}else{tail.setNext(node);}
tail = node;
node.setNext(head);
我想我的问题是：这不是以循环方式实现的吗？
再次有可能我完全不知道我在说什么，但是据我所知，这实际上是一个循环链表。
在此先感谢您的帮助！
完整代码（这三个类分别是CircularLinkedQueue，Node和CircularLinkedListTest）：
CircularLinkedQueue：
import java.util.NoSuchElementException;
public class CircularLinkedQueue<T> {
int count = 0;
private Node<T> head = null;
private Node<T> tail = head;
public CircularLinkedQueue(){
Node<T> node = new Node<T>();
tail = node;
}
/* Inserts the specified element into this queue if it is
* possible to do so immediately without violating capacity
* restrictions, returning true upon success and throwing
* an IllegalStateException if no space is currently available.
*/
public boolean add(T element){
try{
Node<T> node = new Node<T>(element);
if(isEmpty() == true){
head = node;
}else{tail.setNext(node);}
tail = node;
node.setNext(head);
count++;
return true;
}catch(Exception all){
Node<T> node = new Node<T>(element);
if(element == null){throw new NullPointerException("Specified
element is null.");}
else if(element.getClass().getName() !=
node.getData().getClass().getName()){
throw new ClassCastException
("Class of specified element prevents it from being added.");
}
return false;
}
}
/* Retrieves, but does not remove, the head of this queue.
* This method differs from peek only in that it throws
* an exception if this queue is empty.
*/
public T element(){
Node<T> cursor;
if(isEmpty() != true){
cursor = head;
}else{throw new NoSuchElementException("No such element exists.");}
return cursor.getData();
}
/*
Inserts the specified element into this queue if it is possible
to do so immediately without violating capacity restrictions.
When using a capacity-restricted queue, this method is generally
preferable to add(E), which can fail to insert an element only
by throwing an exception.
/*
public boolean offer(T element){
try{
Node<T> node = new Node<T>(element);
if(isEmpty() == true){
head = node;
}else{tail.setNext(node);}
tail = node;
node.setNext(head);
count++;
return true;
}catch(Exception all){return false;}
}
/* Retrieves, but does not remove, the head of this queue,
* or returns null if this queue is empty.
*/
public T peek(){
Node<T> cursor;
//set cursor to head if not empty, create new null node otherwise
if(isEmpty() != true){
cursor = head;
}else{cursor = new Node<T>(); cursor.setData(null);}
//return null if no data is stored
return cursor.getData();
}
/* Retrieves and removes the head of this queue,
* or returns null if this queue is empty.
*/
public T poll(){
Node<T> cursor = head;
if(isEmpty() != true){
if(count <= 1){
head.setNext(null);
head = head.getNext();
tail = head;
count--;
return null;
}else{
//cursor = head;
head = head.getNext();
tail.setNext(head);
}
}else{cursor = new Node<T>(); cursor.setData(null);}
count--;
return cursor.getData();
}
/* Retrieves and removes the head of this queue.
* This method differs from poll only in that it
* throws an exception if this queue is empty.
*/
public T remove(){
Node<T> cursor;
if(isEmpty() != true){
if(count <= 1){
head.setNext(null);
head = head.getNext();
tail = head;
count--;
return null;
}else{
cursor = head;
head = head.getNext();
tail.setNext(head);
}
}
else{throw new NoSuchElementException("No such element exists.");}
count--;
return cursor.getData();
}
//returns whether the list is empty or not
public boolean isEmpty(){return head == null;}
/* This method puts all the values of the circular linked list
* into a String type for output purposes.
*/
@Override
public String toString(){
int cycles = count;
String s = "";
Node<T> cursor = head;
while(cycles > 0){
s = s + cursor.getData() + "\n";
cursor = cursor.getNext();
cycles--;
}
/*
* these lines print as expected & exist only for debugging purposes
System.out.println("next: " + cursor.getNext().getData());
System.out.println("next.next: " +
cursor.getNext().getNext().getData());
System.out.println("next.next.next: " +
cursor.getNext().getNext().getNext().getData());
System.out.println("next.next.next.next: " +
cursor.getNext().getNext().getNext().getNext().getData());
*/
return s;
}
//returns the length of the list
public int getCount(){return count;}
}
节点：
public class Node<T> {
T data;
Node<T> next;
public Node(){data = null;}
public Node(T data){this.data = data;}
public void setData(T data){this.data = data;}
public void setNext(Node<T> nextNode){next = nextNode;}
public T getData(){return data;}
public Node<T> getNext(){return next;}
}
CircularLinkedListTest：
public class CircularLinkedListTest<T>{
public static void main(String[] args) {
/* demonstrates creation of new circular linked lists/linked queues,
* uses two different data types
*/
CircularLinkedQueue<Integer> c1 = new CircularLinkedQueue<Integer>();
CircularLinkedQueue<String> c2 = new CircularLinkedQueue<String>();
//demonstrate add and offer methods detailed in Queue interface
c1.add(3);
c1.offer(45);
c1.offer(71);
c2.add("hello");
c2.offer("good evening");
c2.offer("how do you do");
//demonstrates a toString method and prints after data has been added
System.out.println("c1.toString(): \n" + c1.toString());
System.out.println("c2.toString(): \n" + c2.toString());
/* demonstrates the remove and poll methods, prints out the values in
the list,
* poll method returns null when implemented, isEmpty method shows the
* nodes are truly being removed from the list after poll or remove
methods are
* called
*/
c1.remove();
c2.remove();
c2.remove();
System.out.println("c1.toString(): \n" + c1.toString());
System.out.println("c2.poll(): " + c2.poll());
System.out.println("c2.getCount(): " + c2.getCount());
System.out.println("c2.isEmpty(): " + c2.isEmpty());
System.out.println("");
//re-add data to c2
c2.offer("howdy");
c2.offer("hi there");
//reprint c2, getCount and isEmpty to prove updated data values
System.out.println("c2.toString(): \n" + c2.toString());
System.out.println("c2.getCount(): " + c2.getCount());
System.out.println("c2.isEmpty(): " + c2.isEmpty());
System.out.println("");
/* demonstrate peek and element functions by printing out most
* recent items in the linked queue
*/
System.out.println("c1.peek(): " + c1.peek());
System.out.println("c2.element(): " + c2.peek());
System.out.println("");
//remove items from c1 to show peek returns null when list is empty
c1.remove();
c1.remove();
System.out.println("c1.peek(): " + c1.peek());
System.out.println("c1.getCount(): " + c1.getCount());
System.out.println("c1.isEmpty(): " + c1.isEmpty());
//all methods in queue interface have been demonstrated
}
}
再次感谢您的帮助！
答案 0 :(得分：2)
我在作业中收到的分数为零-根据评分者，我对链表的实现不是循环的。
我发现该评估有些苛刻。 从外部看，您的类表现为循环：它可以在O（1）时间添加新值，并且“最后”值具有指向“首先”，结束循环。
我想我的问题是：这不是以循环方式实现的吗？
在真正的循环实施中， 我不希望看到“头”和“尾”的概念。 毕竟，一个圆圈没有起点也没有终点。 它可能具有当前元素，并具有指向下一个和上一个元素的链接。 也许这就是所需要的。 从内部看， 此实现看起来非常类似于常规链接列表， 快速接近尾巴。 最好问一下平地机！