来自文件路径的Java输入和输出流

Question

How does one use a specified file path rather than a file from the resource folder as an input or output stream? This is the class I have and I would like to read from a specific file path instead of placing the txt file in the resources folder in IntelliJ. Same for an output stream. Any help rendered would be appreciated thanks.

Input Stream

import java.io.*;
import java.util.*;

public class Example02 {
    public static void main(String[] args) throws FileNotFoundException {
        // STEP 1: obtain an input stream to the data

        // obtain a reference to resource compiled into the project
        InputStream is = Example02.class.getResourceAsStream("/file.txt");

        // convert to useful form
        Scanner in = new Scanner(is);

        // STEP 2: do something with the data stream
        // read contents
        while (in.hasNext()) {
            String line = in.nextLine();
            System.out.println(line);
        }

        // STEP 3: be polite, close the stream when done!
        // close file
        in.close();
    }
}

Output stream

import java.io.*;

public class Example03
{
    public static void main(String []args) throws FileNotFoundException
    {
        // create/attach to file to write too
        // using the relative filename will cause it to create the file in
        // the PROJECT root
        File outFile = new File("info.txt");

        // convert to a more useful writer
        PrintWriter out = new PrintWriter(outFile);

        //write data to file
        for(int i=1; i<=10; i++)
            out.println("" + i + " x 5 = " + i*5);

        //close file - required!
        out.close();            
    }
}

Answer 1

Preferred way for getting InputStream is java.nio.file.Files.newInputStream(Path)

try(final InputStream is = Files.newInputStream(Paths.get("/path/to/file")) {
    //Do something with is
}

Same for OutputStream Files.newOutputStream()

try(final OutputStream os = Files.newOutputStream(Paths.get("/path/to/file")) {
    //Do something with os
}

Generally, here is official tutorial from Oracle to working with IO.

Answer 2

First you have to define the path you want to read the file from, absolute path like so:

String absolutePath = "C:/your-dir/yourfile.txt"
InputStream is = new FileInputStream(absolutePath);

It's similar for writing the file as well:

String absolutePath = "C:/your-dir/yourfile.txt"
PrintWriter out = new PrintWriter(new FileOutputStream(absolutePath));

Answer 3

您可以将文件对象用作：

File input = new File("C:\\[Path to file]\\file.txt");