Java中的单链列表存在一些问题

Question

I am attempting to create a singly linked list where I can add nodes that will have an integer value and a next value. I need to be able to traverse this list so I can add the elements of the list. Everything needs to be within one file. I am new to java and could use some assistance. Here is my code:

package LargestSum;
import java.io.*;
import java.util.Scanner;

public class LargestSum {
   public static class LinkedList {

private int num;
private LinkedList node;    
private LinkedList head;
private LinkedList tail;
private int listSize;
public LinkedList next;

public LinkedList(){

    node = null;
    num = 0;
    head = null;
    tail = null;
    listSize = 0;
}

public void setLink(LinkedList l){
    node = l;
}

public void setNum(int n){
    num = n;
}

public LinkedList getNode(){
    return node;
}
public int getNum(){
    return num;
} 

public boolean empty(){
    return head == null;
}

public int getListSize(){
    return listSize;
}

public void insert(int set){
    LinkedList list = new LinkedList();
    listSize++;
    if(head == null){
        head = list;
        tail = head;

    }
    else {
        tail.setLink(list);
        tail = list;
    }
 }
 }

public static void main(String[] args)  throws IOException {
     String fileName = "in.txt";
     LinkedList list = new LinkedList();
     Scanner numbers = new Scanner(new File(fileName));
     while(numbers.hasNext()){
        int num = numbers.nextInt();
        list.insert(num);
        System.out.println(num);
     } 
     int listSize = list.getListSize();
} 
}

I'd appreciate any type of help and pointers, please. Thank you.

Answer 1

Problem in your code is you are initializing linkedlist every time you add an element. so every node are not linked with each other. what you can do is make two classes: 1) node and 2) LinkedList

node will act has container element which denote element in LinkedList. LinkedList class will have all the functionality which you want to do.

I have made changes in your code instead pasting whole new code. so that you can understand difference between them by comparing your code with it.

//package LargestSum;
import java.io.*;
import java.util.Scanner;

public class Test {

    public static class node{
        int num;
        node next;

        public node(int num){
            this.num = num;
            next = null;
        }
        public node getNext(){
            return next;
        }
        public void setNext(node t){
            this.next = t;
        }
        public int getNum(){
            return this.num;
        }
    }


   public static class LinkedList {

//private int num;
//private LinkedList node;    
private node head;
private node tail;
private int listSize;
//public LinkedList next;

public LinkedList(){

//    node = null;
//    num = 0;
    head = null;
    tail = null;
    listSize = 0;
}

//public void setLink(LinkedList l){
//    node = l;
//}

//public void setNum(int n){
//    num = n;
//}

//public LinkedList getNode(){
//    return node;
//}
//public int getNum(){
//    return num;
//} 

public boolean empty(){
    return head == null;
}

public int getListSize(){
    return listSize;
}

public void print(){
    node traverse = head; 
    while(traverse!=null){
        System.out.println(traverse.getNum());
        traverse = traverse.getNext();
    }

}

public void insert(int set){
  //  LinkedList list = new LinkedList();
  node temp = new node(set);

    listSize++;
    if(head == null){       
        head = temp;
        tail = temp;
    }
    else {
        tail.setNext(temp);
        tail = tail.getNext();
    }
 }
 }

public static void main(String[] args)  throws IOException {
    // String fileName = "in.txt";
     LinkedList list = new LinkedList();
     Scanner numbers = new Scanner(System.in);
     int x=10;
     while(x >0){
        int num = numbers.nextInt();
        list.insert(num);
        System.out.println("++++++++++++++++++++++++++++++++++++++++++++");
        list.print();
        x--;
     } 
        System.out.println("++++++++++++++++++++++++++++++++++++++++++++");
        list.print();
     int listSize = list.getListSize();
} 
}

Here, I have implemented very basic one. you can't add other functionality in this code directly. if you want to add other one just use this type of two classes as I used here and add functions in LinkedList class.

If you have any further query comment me.

Thanks,

Bhavik