DLList：我的函數不會產生預期的輸出

Question

對於數據結構課程，我創建了一個基於此DLList Tutorial的DLList程序。我做了兩個功能displayWithForLoop()和display()。我希望他們能夠產出相同的產出，但他們沒有。這是爲什麼？

public class DLList<E> { 
    Node dummy, head, tail; 
    int size; 

    public DLList() { 
     size = 0; 
    } 

    class Node { 
     E element; 
     Node next; 
     Node prev; 

     public Node(E element, Node next, Node prev) { 
      this.element = element; 
      this.next = next; 
      this.prev = prev; 
     } 
    } 

    public void pushNode(E item) { 
     Node newNode = newNode(item, head, dummy); 
     if(head != null) head.prev = newNode; 
     head = newNode; 

     if(tail == null) = newNode; 
     size++; 
     System.out.println("pushing: " + element); 
    } 

    public void display() { 
     System.out.println("iterating forward..."); 
     Node pointer = head; 
     while (pointer != null) { 
      System.out.println(pointer.element); 
      pointer = pointer.next; 
     } 
    } 

    public displayWithForLoop() { 
     Node pointer = head; 
     for(int i = 0; i < size -1; i++) { 
      pointer = pointer.next; 
      System.out.println(pointer.element); 
     } 
    } 

    public static void main(String args[]) { 
     DLList<Integer> list = new DLList<Integer>(); 
     list.pushNode(15); 
     list.pushNode(25); 
     list.pushNode(35); 

     list.displayWithForLoop(); 
     System.out.println("***"); 
     list.display(); 

    } 
} 

我的輸出是： pushing: 15 pushing: 25 pushing: 35 3 25 15 *** iterating forward.. 35 25 15

爲什麼是list.displayWithForLoop（）從list.display（）不同的輸出？

Answer 1

很難說出爲什麼輸出與您呈現的方式不同，但您的displayWithForLoop方法似乎跳過了列表頭部的打印。 您可以在for循環中調換兩個調用的順序：

public displayWithForLoop() { 
    Node pointer = head; 
    for (int i = 0; i < size - 1; i++) { 
     System.out.println(pointer.element); 
     pointer = pointer.next; 
    } 
}