ArrayList 和 BufferedReader 笔记程序

Posted 2023-02-26

【中文标题】ArrayList 和 BufferedReader 笔记程序

【英文标题】：ArrayList and BufferedReader Note Taking Program

【发布时间】：2015-10-01 16:20:18

【问题描述】：

我创建了一个简单的程序，它采用标题和您输入的注释，然后您可以选择使用 BufferedWriter 将注释导出到 txt 文件，但是因为每个注释都是存储在 ArrayList 中的对象当存储它们时，我遍历一个增强循环，当我遍历所有对象时，它会不断复制每个音符。

笔记类

import java.util.*;
public class Notes
 
    private String notes;
    private String titleOfNotes;
    Scanner input = new Scanner(System.in);

    public Notes()
    
        titleOfNote(input);
        takeNotes(input);
    

    public void takeNotes(Scanner x)
    
        System.out.println("Please Enter Your Note");
        notes = x.nextLine();
    

    public void titleOfNote(Scanner y)
       
        System.out.println("Please Enter Title");
        titleOfNotes = y.nextLine();
    
    public String toString()
    
        return "Title: " + titleOfNotes + "\t" + notes; 
    

App Class //完成大部分工作

import java.util.*;
import java.io.*;
public class App

    private int exit = 0; 
    private int createANote;
    private int displayTheNotes; 
    private int inputFromUser;
    public boolean haveFileBeenWritten = true;

    File file = new File("Notes.txt");

    Scanner input = new Scanner(System.in);

    ArrayList<Notes> arrayOfNotes = new ArrayList<Notes>();

    public void makeNoteObject()
    
        arrayOfNotes.add(new Notes());  
    

    public void displayAllTheNote(ArrayList<Notes> n)
    
            for(Notes singleObjectOfNote : n)
            
                System.out.println(singleObjectOfNote);
            
    

    public void programUI()


        while(exit != 1)
           
            System.out.println("1. Create A Note");
            System.out.println("2. Display The Notes");
            System.out.println("3. Exit");
            System.out.println("4. Export to text file");
            System.out.println("Enter Your Operation");
            inputFromUser = input.nextInt();

            if(inputFromUser == 1)
            
                makeNoteObject();
            
            else if(inputFromUser == 2)
            
                displayAllTheNote(arrayOfNotes);
            
            else if(inputFromUser == 3)
               
                System.out.println("Exited");
                exit = 1;
            
            else if(inputFromUser == 4)
            
                makeATxtFileFromNotes(arrayOfNotes); 
                System.out.println("Textfile created filename: " + file.toString()); 
            
            else
            
                System.out.println("You Select A Invalid Command");
            
        
    

    public void makeATxtFileFromNotes(ArrayList<Notes> x)
    

        try (BufferedWriter bw = new BufferedWriter(new FileWriter(file,haveFileBeenWritten)))
        
//Problem here!
            for(Notes singleObjectOfNotes : x)
            
                bw.write(singleObjectOfNotes.toString());
                bw.newLine(); 
            


        catch(IOException e)
        
            System.out.println("Cant Write File: " + file.toString());
            haveFileBeenWritten = false;
        
    

    public App()
    
        programUI();
    
    public static void main(String[]args)
    
        App objectOfApp = new App();

    

我是 Java 新手，所以我的代码不是最好的！

【参考方案1】：

如果您的问题是只需要查看当前列表的Notes 不包括上一个'，那是因为这行：

try (BufferedWriter bw = new BufferedWriter(new FileWriter(file,haveFileBeenWritten)))

默认情况下，haveFileBeenWritten 是 true，因此基于 FileWriter API，它将在现有文件 Notes.txt 上追加，所以如果您不希望这样，请将其更改为 @ 987654328@.

参数：

file - 要写入的 File 对象

append - 如果为真，那么字节将是 写入文件末尾而不是开头

编辑：要访问List<> 元素，请使用get()。

例子：

int size = myList.size();
for (int i = 0 ; i < size ; i++) 
    //...
    Notes note = myList.get(i);
    //...