Java: 文件读取/添加到文件程序未按预期工作（逻辑错误）

Question

我正在尝试编写一个程序：

通过用户给定的文件路径扫描文件
数其数
将其内容打印到终端
通过用户给定的另一个文件路径在新文件中添加

而且它还可以统计新文件的字数，并将其内容打印到终端。

但是这个新文件有两个问题： 1-它只保存我的添加而没有旧文件的内容（即使我使用了 .concat() 方法） 2- 它无法计算新文件的字数。

除此之外，我尝试了很多方法来解决这些问题，但我不能...

package com;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.io.FileWriter;
import java.io.IOException;

public class FileReader {
  public static void main(String[] args) throws IOException {
    Scanner scanTwo = new Scanner(System.in);
    System.out.println("Please Enter Your File Path");
    String filePath = scanTwo.nextLine();  
    File fileInput = new File(filePath);
    Scanner fileScanner = new Scanner(fileInput);
    System.out.println(fileScanner.nextLine());
    System.out.println("Commands: PRINT.FILE --> Prints all file    COUNT.WORDS --> Counts all words   ADD.TO.FILE --> add to selected file");
    System.out.println("Type Command:");
    
    Scanner scan = new Scanner(System.in);
    String printFileCommand = scan.nextLine();
     
     
     if (printFileCommand.contains("PRINT.FILE")) {
       while (fileScanner.hasNextLine()) {
         System.out.println(fileScanner.nextLine());
        }
      } else if (printFileCommand.contains("COUNT.WORDS")) {
        int wordCount = 0;
        while (fileScanner.hasNext()) {
          String fileWords = fileScanner.next();
          wordCount++;
        }
        System.out.println(wordCount);
      } else if (printFileCommand.contains("ADD.TO.FILE")) {
        System.out.println("Please Enter Your new file path");
        String newFilePath = scan.nextLine();
        FileWriter addToFile = new FileWriter(newFilePath);
        System.out.println("Please Enter Your Additions: ");
        String newFileContent = scan.nextLine();
        File newFileInput = new File(newFilePath);
        Scanner newFileScanner = new Scanner(newFileInput); 
        while (newFileScanner.hasNextLine()) {
          newFileContent = newFileContent.concat(newFileScanner.nextLine() + "\n");
        }
        addToFile.write(newFileContent);
        addToFile.close();
        System.out.println("Commands: PRINT.FILE --> Prints all file    COUNT.WORDS --> Counts all words");
        System.out.println("Please Enter Your Command:");
        String newCommand = scan.nextLine();
        if (newCommand.contains("PRINT.FILE")) {
          while (newFileScanner.hasNextLine()) {
            System.out.println(newFileScanner.nextLine());
           }
        } else if (newCommand.contains("COUNT.WORD")) {
          int newWordCount = 0;
           while (newFileScanner.hasNext()) {
           String newFileWords = newFileScanner.next();
           newWordCount++;
         }
         System.out.println(newWordCount);
        } else {
          System.out.println("COMMAND INVALID!");
        }
        addToFile.close();
        // newFileScanner.close();
      }
      else {
        System.out.println("COMMAND INVALID!");
      }
      scanTwo.close();
      fileScanner.close();
      scan.close();
    } 
  }

Answer 1

您确定打开旧文件进行读取和连接吗？我看到你通过 newFilePath 路径打开新文件，但这个文件是空的，这是你的代码：

File newFileInput = new File(newFilePath);
Scanner newFileScanner = new Scanner(newFileInput); 
while (newFileScanner.hasNextLine()) {
    newFileContent = newFileContent.concat(newFileScanner.nextLine() + "\n");
}

此外，如果您已经使用 Scanner 读取文件，则需要创建新的 Scanner 实例 (Resetting a .nextLine() Scanner)

Java: 文件读取/添加到文件程序未按预期工作（逻辑错误）

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