链接列表：无法正常工作

Question

I created a singly linked list , it giving below error . not sure what is wrong, ant suggestion

Error/ OP - List is javaTest.LinkedListcreation@1540e19d

I am not sure what this value in Output is meant for .

Process finished with exit code 0

public  class LinkedList{

public static  void main (String[] a){
    LinkedListcreation L1 = new LinkedListcreation();
    L1.addNodeAtEnd("1");
    System.out.print("List is " + L1);
}

}

class LinkedListcreation {

int listcount;
node head;

LinkedListcreation() {
    head = new node(0);
    listcount=0;
}


node Temp;

void addNodeAtEnd(Object d){
    node Current = head;
    Temp = new node(d);
    while (Current.getNext()!= null){
        Current = Current.getNext();
    }

    Current.setNext(Temp);

    listcount++;
}

}


class node {

Object data;
node next;

node(Object d) {
    next = null;
    this.data=d;
}

node(Object d, node nextNode) {
    next = nextNode;
    this.data=d;
}

   public Object getdata(){
   return data;
   }


public void setdata(int d){
    data = d;
}

public node getNext(){
    return next;
}

public void setNext (node nextValue){
    next = nextValue;
}
}

Answer 1

Your code is all right, but in order to print useful information about an object (your list in this example), you need to override the toString method in your LinkedListcreation class.

For example:

public String toString() {
    return "List with " + this.listcount + " nodes.";
}

Answer 2

you are trying to print the list object rather than the element which you have added and more over what you see is not error. check about toString() method in java to understand the output which you see.

Modify your main() as below to see the element you added.

 public static  void main (String[] a){
   LinkedListcreation L1 = new LinkedListcreation();
  L1.addNodeAtEnd("1");
   System.out.print("List is " + L1.head.next.data);

}

output : List is 1

Answer 3

As everybody said, you have to override toString() . Here you have the right implementation:

public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("[");
    sb.append(head.data.toString());

    node n;
    while(n = head.getNext() != null)
        sb.append(", " + n.data.toString());

    sb.append("]");
    return sb.toString();
}

Answer 4

Your code does not have any error. If you want to print the nodes in your list you just have to add another function in you LinkedListcreation class which will iterate over your list and print each node's data. Add this block in your LinkedListcreation class.

public void printList(){
node current = head.next;
while(current!=null){
    System.out.println("node's data is: "+ current.getdata());
    current = current.getNext();
}

}

Also in your main function call the above mentioned function using your list's object L1.

L1.printList();

Answer 5

The code has compiler errors. Try corrected code below

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

namespace ConsoleApplication1
{
    class LinkedList
    {

        static void Main(String[] a){
           LinkedListcreation L1 = new LinkedListcreation();
           L1.addNodeAtEnd("1");
           Console.WriteLine("List is " + L1);
        }

    }

    public class LinkedListcreation
    {

        int listcount;
        node head;

        public LinkedListcreation()
        {
            head = new node(0);
            listcount = 0;
        }


        node Temp;

        public void addNodeAtEnd(Object d)
        {
            node Current = head;
            Temp = new node(d);
            while (Current.getNext() != null)
            {
                Current = Current.getNext();
            }

            Current.setNext(Temp);

            listcount++;
        }

    }


    public class node
    {

        Object data;
        node next;

        public node(Object d)
        {
            next = null;
            this.data = d;
        }

        node(Object d, node nextNode)
        {
            next = nextNode;
            this.data = d;
        }

        public Object getdata()
        {
            return data;
        }


        public void setdata(int d)
        {
            data = d;
        }

        public node getNext()
        {
            return next;
        }

        public void setNext(node nextValue)
        {
            next = nextValue;
        }
    }

}
​