Java类与泛型数据类型

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英文:

Java class with generic data types

问题

我正在尝试编写一个简单的链表类，该类使用了泛型数据类型。我是Java的新手，所以我不知道如何调试主方法中出现的错误消息，该错误消息在我尝试将数据插入我的类的实例时出现。类代码和主方法如下所示：

  1. import java.io.*;
  3. // Java program to implement
  4. // a Singly Linked List
  5. public class MyLinkedList<T> {
  6. 	
  8. 	 Node head; // 链表的头部
  9. 	 class Node<T> {
  10. 	
  11. 	 T data;
  12. 	 Node next;
  13. 	 // 构造函数
  14. 		 Node(T d)
  15. 		 {
  16. 		     data = d;
  17. 		     next = null;
  18. 		 }
  19. 		 }
  20. 	  
  21. 	    // 插入新节点的方法
  22. 	MyLinkedList insert(MyLinkedList list, T data)
  23. 	{ 
  24. 	    // 使用给定数据创建一个新节点
  25. 	        Node new_node = new Node(data); 
  26. 	        new_node.next = null; 
  27. 	  
  28. 	        // 如果链表为空，
  29. 	    // 则将新节点设为头部
  30. 	    if (list.head == null) { 
  31. 	        list.head = new_node; 
  32. 	    } 
  33. 	    else { 
  34. 	        // 否则遍历到最后一个节点
  35. 	        // 并在那里插入新节点
  36. 	            Node last = list.head; 
  37. 	            while (last.next != null) { 
  38. 	                last = last.next; 
  39. 	            } 
  40. 	  
  41. 	            // 在最后一个节点处插入新节点
  42. 	            last.next = new_node; 
  43. 	        } 
  44. 	  
  45. 	        // 通过头部返回链表
  46. 	    return list; 
  47. 	}    
  48. 	// 驱动程序代码
  49. 	public static void main(String[] args) 
  50. 	{ 
  51. 	    /* 从空链表开始。 */
  52. 	    MyLinkedList list = new MyLinkedList();
  53. 	    
  54. 	    // 插入值
  55. 	    list = insert(list, 1);
  56. 	} 
  57. }

请注意，我已经修复了代码中的HTML编码错误，使其在Java中正常运行。

英文:

I am trying to write a simple linked list class that uses generic data type. I am new to Java so I can't figure out how to debug the error message in the main method that arises when I try to insert data into an instance of my class. The class code and the main method are as follows:

  1. import java.io.*; 
  2. // Java program to implement 
  3. // a Singly Linked List 
  4. public class MyLinkedList&lt;T&gt; {
  5. Node head; // head of the list
  6. class Node&lt;T&gt; {
  7. T data;
  8. Node next;
  9. // Constructor
  10. Node(T d)
  11. {
  12. data = d;
  13. next = null;
  14. }
  15. }
  16. // Method to insert a new node 
  17. MyLinkedList insert(MyLinkedList list, T data)
  18. { 
  19. // Create a new node with given data 
  20. Node new_node = new Node(data); 
  21. new_node.next = null; 
  22. // If the Linked List is empty, 
  23. // then make the new node as head 
  24. if (list.head == null) { 
  25. list.head = new_node; 
  26. } 
  27. else { 
  28. // Else traverse till the last node 
  29. // and insert the new_node there 
  30. Node last = list.head; 
  31. while (last.next != null) { 
  32. last = last.next; 
  33. } 
  34. // Insert the new_node at last node 
  35. last.next = new_node; 
  36. } 
  37. // Return the list by head 
  38. return list; 
  39. }    
  40. // Driver code 
  41. public static void main(String[] args) 
  42. { 
  43. /* Start with the empty list. */
  44. MyLinkedList list = new MyLinkedList();
  45. // Insert the values 
  46. list = insert(list, 1);
  47. } 
  48. }

答案1

得分: 3

  1. 你需要在类声明和方法签名中将 int 改为 T。
  1. class MyLinkedList<T> {
  2.     MyLinkedList() {
  3.         head = null;
  4.     }
  5.     Node<T> head; // head of list
  6.     class Node<T> {
  8.         T data;
  9.         Node<T> next;
  11.         // Constructor
  12.         Node(T d) {
  13.             data = d;
  14.             next = null;
  15.         }
  16.     }
  18.     // Method to insert a new node
  20.     public void insert(T data) {
  21.         // Create a new node with given data
  22.         Node<T> new_node = new Node<T>(data);
  23.         new_node.next = null;
  25.         // If the Linked List is empty,
  26.         // then make the new node as head
  27.         if (this.head == null) {
  28.             this.head = new_node;
  29.         } else {
  30.             Node<T> last = this.head;
  31.             while (last.next != null) {
  32.                 last = last.next;
  33.             }
  34.             // Insert the new_node at last node
  35.             last.next = new_node;
  36.         }
  37.     }
  39.     protected void display() {
  40.         Node<T> myNode = head;
  41.         System.out.println();
  42.         while (myNode != null) {
  43.             System.out.println(myNode.data);
  44.             myNode = myNode.next;
  45.         }
  46.     }
  47. }
  1. 将 insert 方法的签名更改如下：
  1. public static void main(String[] args) {
  2.     /* Start with the empty list. */
  3.     MyLinkedList<Integer> list = new MyLinkedList<Integer>();
  5.     // Insert the values
  6.     list.insert(1);
  7.     list.insert(3);
  8.     list.insert(12);
  9.     list.insert(11);
  10.     list.insert(21);
  11.     list.insert(22);
  12.     list.insert(45);
  13.     list.display();
  14. }
  1. 为了编码清晰和理解，我已将类名更改为 MyLinkedList。
英文:

  1. You need to change int to T in class declaration and method signature.

    1.  class MyLinkedList&lt;T&gt; {
    2. MyLinkedList() {
    3. head=null;
    4. }
    5. Node head; // head of list
    6. class Node&lt;T&gt; {
    7. T data;
    8. Node next;
    9. // Constructor
    10. Node(T d) {
    11. data = d;
    12. next = null;
    13. }

    }

    // Method to insert a new node

    1. public void insert(T data) {
    2. // Create a new node with given data
    3. Node new_node = new Node(data);
    4. new_node.next = null;
    5. // If the Linked List is empty,
    6. // then make the new node as head
    7. if (this.head == null) {
    8. this.head = new_node;
    9. } else {
    10. Node last = this.head;
    11. while (last.next != null) {
    12. last = last.next;
    13. }
    14. // Insert the new_node at last node
    15. last.next = new_node;
    16. }

    }

    1.  protected void display() {
    2. Node myNode=head;
    3. System.out.println();
    4. while (myNode != null) {
    5. System.out.println(myNode.data);
    6. myNode=myNode.next;
    7. }

    }

  2. Change the insert method signature to the below:

    1. public static void main(String[] args) {
    2. /* Start with the empty list. */
    3. MyLinkedList&lt;Integer&gt; list = new MyLinkedList&lt;Integer&gt;();
    4. // Insert the values
    5. list.insert(1);
    6. list.insert(3);
    7. list.insert(12);
    8. list.insert(11);
    9. list.insert(21);
    10. list.insert(22);
    11. list.insert(45);
    12. list.display();
    13. }

  3. For clear coding and understanding I have changed class name as MyLinkedList

huangapple
  • 本文由 发表于 2020年7月30日 16:45:51
  • 转载请务必保留本文链接：https://go.coder-hub.com/63169484.html
  • java
  • nested-generics
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