如何从 Java 中 Main 类的相对路径读取文件？

Question

On the same directory of my Main.java file, I have a package/folder named database , and inside the database package I have a file named Data.txt .

This is my code of Main.java , but it is throwing this error:

java: exception java.io.FileNotFoundException

How can I get the file from a relative file? I'm used to web development, and usually something with a . dot like "./folder/file.txt" works.

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

    public class Main {

        public static void main(String[] args) {

            readFile();

        }

        public static void readFile() {

            File file = new File("./database/Data.txt");
            Scanner scanner = new Scanner(file);

            try {

                while (scanner.hasNextLine()) {
                    int i = scanner.nextInt();
                    System.out.println(i);
                }
                scanner.close();
            }
            catch (FileNotFoundException e) {
                e.printStackTrace();
            }

        }

    }

Answer 1

You are not importing FileNotFoundException class. also, scanner statement throws the exception which should inside try. Solution is as below.

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

public class Main {

    public static void main(String[] args) {

        readFile();

    }

    public static void readFile() {

        File file = new File("database/Data.txt");

        try {
            Scanner scanner = new Scanner(file);
            while (scanner.hasNextLine()) {
                int i = scanner.nextInt();
                System.out.println(i);
            }
            scanner.close();
        }catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }

}

Only check if those content can read using scanner or not. Content having int properly. otherwise it will throw java.util.InputMismatchException.

Answer 2

Are you working on a mac or windows system. I am on windows and ".\database\Data.txt" would most probably work depending on where the file is in your file structure.