java - 如何从java中的链表中删除一个对象？

Question

我的代码有一个问题，我做了一个示例程序来显示链接列表中的 emp 详细信息，现在当我尝试删除特定条目时出现问题意味着它不起作用，我希望我在代码中犯了一些错误你能建议怎么做吗？

import java.util.*;

class EmpDedup {
    int record;
    String fprint;
    int fid;

    EmpDedup(int record, String fprint, int fid) {
        this.record = record;
        this.fprint = fprint;
        this.fid = fid;
    }

    public int getRecord() {
        return record;
    }

    public String getFprint() {
        return fprint;
    }

    public int getFid() {
        return fid;
    }

    public static void main(String[] args) {
        int count = 0;
        LinkedList<EmpDedup> list = new LinkedList<EmpDedup>();
        list.add(new EmpDedup(101, "entry1", 20));
        list.add(new EmpDedup(102, "entry2", 30));
        list.add(new EmpDedup(103, "entry3", 40));
        list.add(new EmpDedup(104, "entry4", 50));

        Scanner input = new Scanner(System.in);
        System.out.print("Enter record no to display: ");
        int rec = input.nextInt();
        for (EmpDedup data : list) {
            if (data.getRecord() == rec) {
                System.out.println(data.getRecord() + "\t" + data.getFprint() + "\t" + data.getFid() + "\t");

                count++;

            }
        }
        System.out.println("The size of an linkedlist is: \t" + list.size());

        System.out.println("The number of  available record  is :" + count);

        System.out.println("The size of an linkedlist is: \t" + list.size());
        Scanner input1 = new Scanner(System.in);
        System.out.print("Enter record no to delete: ");// here i try to delete a particular record
        int rec1 = input1.nextInt();
        for (EmpDedup data : list) {
            if (data.getRecord() == rec1) {
                // System.out.println(data.getRecord()+"\t"+data.getFprint()+"\t"+data.getFid()+"\t");
                list.remove(data); // problem is here
                count++;

            }
        }
    }
}

Answer 1

当您对它们进行迭代时，您不能在列表中操作（添加、删除...项目）。您必须使用迭代器

for(Iterator<EmpDedup> iter = list.iterator(); iter.hasNext();) {
    EmpDedup data = iter.next();
    if (data.getRecord() == rec1) {
        iter.remove();
    }
}

请参阅http://docs.oracle.com/javase/6/docs/api/java/util/Iterator.html

Answer 2

使用 anIterator代替，然后使用上的remove()方法Iterator

Answer 3

当你这样做时：

list.remove(101);

您正在调用此方法，这将不符合您的目的。

你应该使用：

list.remove(data);

Answer 4

您尝试删除索引为 101 的元素，但列表中只有 4 个项目。它如何删除索引为 101 的元素？

如果要删除等于 EmpDedup(101,"entry1",20) 的元素，则必须传入 remove 方法这个对象。不要忘记重新定义 EmpDedup 的 equals 和 hash 码。

Answer 5

该代码尝试删除索引位置 101 处的元素，但列表中只有四个项目。

使用以下代码替换您的代码：

for( EmpDedup data : list)
{
   if( data.getRecord() == rec1 )
   {
        list.remove( data );     
         ++count;
    }
}

这就是列表对象将被删除的地方。

Answer 6

for( EmpDedup data:list)
{
   if(data.getRecord()==rec1)
   {
        list.remove(data);     
         count++;

    }
 }

Answer 7

导入 java.util.Scanner；

// 一个完整的工作 Java 程序来演示单个删除 // 链表 class LinkedList { Node head; // 列表头

/* Linked list Node*/
class Node
{
    int data;
    Node next;
    Node(int d)
    {
        data = d;
        next = null;
    }
}

/* Given a key, deletes the first occurrence of key in linked list */
void deleteNode(int key)
{
    // Store head node
    Node temp = head, prev = null;

    // If head node itself holds the key to be deleted
    if (temp != null && temp.data == key)
    {
        head = temp.next; // Changed head
        return;
    }

    // Search for the key to be deleted, keep track of the
    // previous node as we need to change temp.next
    while (temp != null && temp.data != key)
    {
        prev = temp;
        temp = temp.next;
    }    

    // If key was not present in linked list
    if (temp == null) return;

    // Unlink the node from linked list
    prev.next = temp.next;
}

/* Inserts a new Node at front of the list. */
public void push(int new_data)
{
    Node new_node = new Node(new_data);
    new_node.next = head;
    head = new_node;
}

/* This function prints contents of linked list starting from
    the given node */
public void printList()
{
    Node tnode = head;
    while (tnode != null)
    {
        System.out.print(tnode.data+" ");
        tnode = tnode.next;
    }
}

/* Drier program to test above functions. Ideally this function
should be in a separate user class. It is kept here to keep
code compact */
public static void main(String[] args)
{
    LinkedList llist = new LinkedList();

    llist.push(7);
    llist.push(1);
    llist.push(3);
    llist.push(2);

    System.out.println("\nCreated Linked list is:");
    llist.printList();

    Scanner sc = new Scanner(System.in);
    System.out.println("please enter input");
    int aa =sc.nextInt();
    llist.deleteNode(aa); // Delete node at position 4

    System.out.println("\nLinked List after Deletion at position :"+aa);


    llist.printList();

    System.out.println("adding element to the LinkedList");

    System.out.println("enter element");
    int dd = sc.nextInt();
    llist.push(dd);

    llist.printList();
}

}