Read/Write files in java, python 3, c++ and javascript

Here's how you can read and write files in Java, Python, C++, and JavaScript:

In Java, you can use the "BufferedReader" and "FileReader" classes to read a file, and the "BufferedWriter" and "FileWriter" classes to write a file. Here is some example code that reads a file line by line and prints each line to the console:

import java.io.*; 
public class FileExample { 
    public static void main(String[] args) { 
        try { 
            // Open the file 
            FileReader fr = new FileReader("input.txt"); 
            BufferedReader br = new BufferedReader(fr); 
            // Read the file line by line 
            String line; 
            while ((line = br.readLine()) != null) {
    
                        System.out.println(line); 
            } 
            // Close the file 
            br.close(); 
        } catch (IOException e) { 
            e.printStackTrace(); 
        } 
    } 
}

To write to a file, you can use similar code, but with the "BufferedWriter" and "FileWriter" classes instead:

import java.io.*; 
public class FileExample { 
    public static void main(String[] args) { 
        try { 
            // Open the file 
            FileWriter fw = new FileWriter("output.txt"); 
            BufferedWriter bw = new BufferedWriter(fw); 
            // Write to the file 
            bw.write("Hello, world!"); 
            bw.newLine(); 
            bw.write("This is a test."); 
            // Close the file 
            bw.close(); 
        } catch (IOException e) { 
            e.printStackTrace(); 
        } 
    } 
}

In Python, you can use the "open" function to open a file for reading or writing, and the "read" or "write" methods to read or write to the file. Here is some example code that reads a file line by line and prints each line to the console:

with open("input.txt") as f: 
    for line in f: 
        print(line)

To write to a file, you can use similar code, but with the "w" mode and the "write" method instead:

with open("output.txt", "w") as f: 
    f.write("Hello, world!\n") 
    f.write("This is a test.\n")

In C++, you can use the "ifstream" and "ofstream" classes to read and write files. Here is some example code that reads a file line by line and prints each line to the console:

#include <iostream> 
#include <fstream> 
#include <string> 
using namespace std; 
int main() { 
    // Open the file 
    ifstream in("input.txt"); 
    // Read the file line by line 
    string line; 
    while (getline(in, line)) { 
        cout << line << endl; 
    } 
    // Close the file 
    in.close(); 
    return 0; 
}

To write to a file, you can use similar code, but with the "ofstream" class instead:

#include <iostream> 
#include <fstream> 
#include <string> 
using namespace std; 
int main() { 
    // Open the file 
    ofstream out("output.txt"); 
    // Write to the file 
    out << "Hello, world!" << endl;
  out << "This is a test." << endl; 
    // Close the file 
    out.close(); 
    return 0; 
}

In JavaScript, to read and write files in JavaScript, you can use the "fs" module, which provides an API for interacting with the file system.

Here is some example code that reads a file line by line and prints each line to the console:

const fs = require("fs"); 
fs.readFile("input.txt", "utf-8", (error, data) => { 
    if (error) { 
        console.error(error); 
        return; 
    } 
    console.log(data); 
});

To write to a file, you can use the "writeFile" method, like this:

const fs = require("fs"); 
fs.writeFile("output.txt", "Hello, world!\nThis is a test.\n", error => { 
    if (error) { 
        console.error(error); 
        return; 
    } 
    console.log("File written successfully."); 
});

The "fs" module also provides other methods for reading and writing files, such as "readFileSync" for synchronous file reading and "appendFile" for appending data to an existing file. You can find more information about these methods in the documentation for the "fs" module: https://nodejs.org/api/fs.html

I hope this helps! Let me know if you have any questions or need further clarification.