Different ways to read and write data of files in Java

Using FileInputStream and FileOutputStream classes:

// Reading data from file
File file = new File("filename.txt");
try (FileInputStream fis = new FileInputStream(file)) {
    byte[] data = new byte[(int) file.length()];
    fis.read(data);
    String fileContent = new String(data, "UTF-8");
}

// Writing data to file
String content = "Hello, world!";
try (FileOutputStream fos = new FileOutputStream(file)) {
    fos.write(content.getBytes());
}

Using BufferedReader and BufferedWriter classes:

// Reading data from file
File file = new File("filename.txt");
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
}

// Writing data to file
String content = "Hello, world!";
try (BufferedWriter bw = new BufferedWriter(new FileWriter(file))) {
    bw.write(content);
}

Using Scanner class:

// Reading data from file
File file = new File("filename.txt");
try (Scanner scanner = new Scanner(file)) {
    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        System.out.println(line);
    }
}

// Writing data to file
String content = "Hello, world!";
try (PrintWriter writer = new PrintWriter(file)) {
    writer.print(content);
}

Note that these methods throw IOException in case of any I/O error. Also, it’s important to close the stream after using it to avoid any resource leaks.