将文本文件输入插入链表

Question

嘿伙计们，我正在尝试从文本文件中读取并将每个名称存储到链表节点中。 当我在文本文件中读取时，它会读取该行，这是一个名称。 我正在尝试将每个名称存储到链表节点中。 当我调用 insertBack 方法并将其打印出来时，它表明节点中没有任何内容。 谁能指出我正确的方向，将不胜感激？

这是文件在类中：

import java.util.Scanner;
import java.io.*;
public class fileIn {
    String fname;
    public fileIn() {
        getFileName();
        readFileContents();
    }
    public void readFileContents()
    {
        boolean looping;
        DataInputStream in;
        String line;
        int j, len;
        char ch;
        /* Read input from file and process. */
        try {
            in = new DataInputStream(new FileInputStream(fname));
            LinkedList l = new LinkedList();
            looping = true;
            while(looping) {
                /* Get a line of input from the file. */
                if (null == (line = in.readLine())) {
                    looping = false;
                    /* Close and free up system resource. */
                    in.close();
                }
                else {
                    System.out.println("line = "+line);
                    j = 0;
                    len = line.length();
                    for(j=0;j<len;j++){
                        System.out.println("line["+j+"] = "+line.charAt(j));
                    }
                }
                l.insertBack(line);
            } /* End while. */
        } /* End try. */
        catch(IOException e) {
            System.out.println("Error " + e);
        } /* End catch. */
    }
    public void getFileName()
    {
        Scanner in = new Scanner(System.in);
        System.out.println("Enter file name please.");
        fname = in.nextLine();
        System.out.println("You entered "+fname);
    }
}

这是 LinkedListNode 类：

public class LinkedListNode
{
    private String data;
    private LinkedListNode next;

    public LinkedListNode(String data)
    {
        this.data = data;
        this.next = null;
    }
    public String getData()
    {
        return data;
    }
    public LinkedListNode getNext()
    {
        return next;
    }
    public void setNext(LinkedListNode n)
    {
        next = n;
    }
}

最后是具有 main 方法的 LinkedList 类：

import java.util.Scanner;
public class LinkedList {
    public LinkedListNode head;
    public static void main(String[] args) {
        fileIn f = new fileIn();
        LinkedList l = new LinkedList();
        System.out.println(l.showList());   
    }
    public LinkedList() {
        this.head = null;
    }
    public void insertBack(String data){
        if(head == null){
            head = new LinkedListNode(data);
        }else{
            LinkedListNode newNode = new LinkedListNode(data);
            LinkedListNode current = head;
            while(current.getNext() != null){
                current = current.getNext();
            }
            current.setNext(newNode);
        }       
    }
    public String showList(){
        int i = 0;
        String retStr = "List nodes:n";
        LinkedListNode current = head;
        while(current != null){
            i++;
            retStr += "Node " + i + ": " + current.getData() + "n";
            current = current.getNext();
        }
        return retStr;
    }
}

Answer 1

问题是您在fileIn中创建LinkedList。

但是你不导出它：

  fileIn f = new fileIn();
  LinkedList l = new LinkedList();

你需要的是这样的东西：

  fileIn f = new fileIn();
  LinkedList l = f.readFileContents(String filename, new LinkedList()); 

更改方法以使用您创建的LinkedList，然后填充它。因此，fileIn类可能如下所示：

public class fileIn {
    ...
    public void readFileContents(String fileName, LinkedList) {
        // fill linked list
    }
    ...
}