java - 在Java中跟踪ListNode的头

Question

我目前正在开发自己的名为 LString 的 Java 类，该类旨在在字符链接列表和字符串之间来回转换。

我的 toString() 方法遇到问题，特别是跟踪链接列表的“头”，以便循环遍历它并将字符连接到新字符串中。在研究时，我读到我应该以某种方式跟踪列表的头部，但我不知道如何实现它。

任何帮助将不胜感激!

编辑:我收到的错误消息是:

LString.java:79: 错误:找不到符号
ListNode 当前 = this.front;

public class LString{


   private static int length;
   // ListNode constructors

   // Creates a new ListNode with characters stored in variable "data" and 
   // Node named next
   private class ListNode{
      char item;
      ListNode next;


      private ListNode(){
      }

      // creates a new ListNode that has the value and links to the specified ListNode
      private ListNode(char item, ListNode next){
         this.item = item;
         this.next = next;
      }

      // given a character, creates a new ListNode that doesn't link to anything
      private ListNode(char item){
         this.item = item;
         this.next = null;
      }


   }


   public LString(){
      this.length = 0;
      ListNode front = new ListNode();
   }

   //LString
   // Takes in a String object and loops until it has added all characters to a new linked list
   public LString(String original){

      ListNode front;
      this.length = 1;                           // length keeps track of number of nodes

      if (original.charAt(0) == 0){             // creates a new ListNode if it is an empty string
         front = new ListNode();       
      }
      else {
         front = new ListNode(original.charAt(0));
      }


      //System.out.println("this is happening " + front.item);

      //ListNode current = front;  
      for (int index = 1; index < original.length(); index++) {
         front.next = new ListNode(original.charAt(index), front.next);
         front = front.next;
         //System.out.println("strings: " + front.item);
         length++;
      }
         //System.out.println("length: " + length);
   }

   // returns length of the LString object
   public int length(){
      return this.length;
   }

   // toString takes an LString object and converts it to a string
   public String toString(){
      StringBuilder newString;

      ListNode current = this.front;
      while (current.next != null){
         newString.append(current.item);
         current = current.next; 
      }

      return newString.toString();
   }

   public static void main(String[] args){
      LString stuffTest = new LString("hello");
      int valueOf = stuffTest.length();
      System.out.println(stuffTest.length());
      String testMeWhy = stuffTest.toString();

   }





}

Answer 1

通过追加到末尾来构建链表的一般模式是:

开头:

head = null;
tail = null;

要将 newNode 添加到列表中:

if (head == null) {
    head = newNode;
} else {
    tail.next = newNode;
}
tail = newNode;

我认为您正在尝试通过在列表类中仅保留一个指针来实现此目的，但这效果不太好。另外，使用此模式执行操作意味着您不必在列表前面有一个“特殊”节点，除非有其他充分的理由。看起来您试图使用不带参数的 new ListNode() 来创建某种特殊节点，但只是有时。这是不必要的，只会让事情变得更加复杂。