Printwriter FileNotFoundException 异常

Question

我正在尝试编写一个英里跟踪器程序来跟踪用户步行、跑步或游泳的距离。该程序要求用户输入会话期间步行的距离，将其存储在双精度中，从文件中读取有关先前步行总距离的数据，将最近会话的距离添加到过去的总距离以创建新的总距离，并将该总数写入存储它以供将来使用的文件。编写代码时，当我尝试将它们指向文件时，IDE 在打印编写器和扫描仪上显示错误：

Scanner reader = new Scanner(storage); //error at second Scanner
PrintWriter writer = new PrintWriter(storage); // error at second PrintWriter

错误显示为 "FileNotFoundException"

当放在 try 块中时，错误消失，程序在运行:

时打印 catch 块错误报告

catch(FileNotFoundException e){
            System.out.println("Check that the text file is in the correct directory.");
            e.printStackTrace();
        }

这是我使用 PrintWriter 编写的第一个程序，因此我将不胜感激一些关于我做错了什么的指示和解释。

完整代码如下：

import java.io.File;
import java.io.PrintWriter;
import java.io.FileInputStream;
import java.util.Scanner;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.lang.String;

public class Main {

    public static void main(String[] args) {


        //gets interval data from user
        System.out.println("Please type the amount of miles walked.");
        Scanner input = new Scanner(System.in);
        double inMiles = input.nextDouble();


            //creates file and scanner that reads to file

            File storage = new File ("Mile Tracker//Mile.txt");
        try {
            storage.createNewFile();
        }
        catch(IOException e ){
            System.out.println("File not created.");
        }

        try {
            Scanner reader = new Scanner(storage);

            //takes data from file and sets it to a variable
            double Miles = reader.nextDouble();

            double TotalMiles = Miles + inMiles;

            //PrintWriter reader = new PrintWriter( file );


            //PrintWriter that clears the file
            /*PrintWriter clearwriter = new PrintWriter(storage);
            clearwriter.print("");

            clearwriter.close();
*/
            PrintWriter writer = new PrintWriter(storage);
            writer.print(TotalMiles);

            writer.close();
        }
        catch(FileNotFoundException e){
            System.out.println("Check that the text file is in the       correct directory.");
             e.printStackTrace();
        }

     }
}

Answer 1

如果您已经有一个名为 "Mile Tracker" 的目录，请检查它是否与 java class 在同一路径中，因为您没有明确给出 File构造函数。如果你没有"Mile Tracker"目录，那么你修改代码为：

File storage = new File ("Mile Tracker//Mile.txt");
try {
    storage.getParentFile().mkdirs();
    storage.createNewFile();
}
catch(Exception e ){
    System.out.println("File not created.");
}

至此，FileNotFound 错误应该得到解决。

Printwriter FileNotFoundException 异常

Printwriter FileNotFoundException

java

file

printwriter