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:

import java.io.*;

// Java program to implement
// a Singly Linked List
public class MyLinkedList<T> {
	

	 Node head; // 链表的头部
	 class Node<T> {
	
	 T data;
	 Node next;
	 // 构造函数
		 Node(T d)
		 {
		     data = d;
		     next = null;
		 }
		 }
	  
	    // 插入新节点的方法
	MyLinkedList insert(MyLinkedList list, T data)
	{ 
	    // 使用给定数据创建一个新节点
	        Node new_node = new Node(data); 
	        new_node.next = null; 
	  
	        // 如果链表为空,
	    // 则将新节点设为头部
	    if (list.head == null) { 
	        list.head = new_node; 
	    } 
	    else { 
	        // 否则遍历到最后一个节点
	        // 并在那里插入新节点
	            Node last = list.head; 
	            while (last.next != null) { 
	                last = last.next; 
	            } 
	  
	            // 在最后一个节点处插入新节点
	            last.next = new_node; 
	        } 
	  
	        // 通过头部返回链表
	    return list; 
	}    
	// 驱动程序代码
	public static void main(String[] args) 
	{ 
	    /* 从空链表开始。 */
	    MyLinkedList list = new MyLinkedList();
	    
	    // 插入值
	    list = insert(list, 1);
	} 
}

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:

import java.io.*; 
// Java program to implement 
// a Singly Linked List 
public class MyLinkedList&lt;T&gt; {
Node head; // head of the list
class Node&lt;T&gt; {
T data;
Node next;
// Constructor
Node(T d)
{
data = d;
next = null;
}
}
// Method to insert a new node 
MyLinkedList insert(MyLinkedList list, T data)
{ 
// Create a new node with given data 
Node new_node = new Node(data); 
new_node.next = null; 
// If the Linked List is empty, 
// then make the new node as head 
if (list.head == null) { 
list.head = new_node; 
} 
else { 
// Else traverse till the last node 
// and insert the new_node there 
Node last = list.head; 
while (last.next != null) { 
last = last.next; 
} 
// Insert the new_node at last node 
last.next = new_node; 
} 
// Return the list by head 
return list; 
}    
// Driver code 
public static void main(String[] args) 
{ 
/* Start with the empty list. */
MyLinkedList list = new MyLinkedList();
// Insert the values 
list = insert(list, 1);
} 
}

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。
class MyLinkedList<T> {
    MyLinkedList() {
        head = null;
    }
    Node<T> head; // head of list
    class Node<T> {

        T data;
        Node<T> next;

        // Constructor
        Node(T d) {
            data = d;
            next = null;
        }
    }

    // Method to insert a new node

    public void insert(T data) {
        // Create a new node with given data
        Node<T> new_node = new Node<T>(data);
        new_node.next = null;

        // If the Linked List is empty,
        // then make the new node as head
        if (this.head == null) {
            this.head = new_node;
        } else {
            Node<T> last = this.head;
            while (last.next != null) {
                last = last.next;
            }
            // Insert the new_node at last node
            last.next = new_node;
        }
    }

    protected void display() {
        Node<T> myNode = head;
        System.out.println();
        while (myNode != null) {
            System.out.println(myNode.data);
            myNode = myNode.next;
        }
    }
}
  1. 将 insert 方法的签名更改如下:
public static void main(String[] args) {
    /* Start with the empty list. */
    MyLinkedList<Integer> list = new MyLinkedList<Integer>();

    // Insert the values
    list.insert(1);
    list.insert(3);
    list.insert(12);
    list.insert(11);
    list.insert(21);
    list.insert(22);
    list.insert(45);
    list.display();
}
  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.

     class MyLinkedList&lt;T&gt; {
    MyLinkedList() {
    head=null;
    }
    Node head; // head of list
    class Node&lt;T&gt; {
    T data;
    Node next;
    // Constructor
    Node(T d) {
    data = d;
    next = null;
    }
    

    }

    // Method to insert a new node

    public void insert(T data) {
    // Create a new node with given data
    Node new_node = new Node(data);
    new_node.next = null;
    // If the Linked List is empty,
    // then make the new node as head
    if (this.head == null) {
    this.head = new_node;
    } else {
    Node last = this.head;
    while (last.next != null) {
    last = last.next;
    }
    // Insert the new_node at last node
    last.next = new_node;
    }
    

    }

     protected void display() {
    Node myNode=head;
    System.out.println();
    while (myNode != null) {
    System.out.println(myNode.data);
    myNode=myNode.next;
    }
    

    }

  2. Change the insert method signature to the below:

    public static void main(String[] args) {
    /* Start with the empty list. */
    MyLinkedList&lt;Integer&gt; list = new MyLinkedList&lt;Integer&gt;();
    // Insert the values
    list.insert(1);
    list.insert(3);
    list.insert(12);
    list.insert(11);
    list.insert(21);
    list.insert(22);
    list.insert(45);
    list.display();
    }
    
  3. For clear coding and understanding I have changed class name as MyLinkedList

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  • 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
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