How to Write to a File in Java - Methods Explained

Learn how to write to a file in Java using three popular methods: FileOutputStream(), FileWriter.write(), and Files.write(). Each method offers different capabilities for file handling in Java applications.

Write To File in Java

There are multiple ways to write to a file in Java. Below are the three most popular methods:

Using FileOutputStream() constructor
Using FileWriter.write() method
Using Files.write() method

Write To File Using FileOutputStream Constructor

FileOutputStream is used to create a file and write data into it. If the file doesn’t exist, it will be created before opening it for output.

Syntax

The following constructor takes a file name as a string to create an output stream object:

Syntax


OutputStream f = new FileOutputStream("C:/java/hello.txt");

The following constructor takes a file object to create an output stream:

Syntax


File f = new File("C:/java/hello.txt");
OutputStream f = new FileOutputStream(f);
for (int x = 0; x < bWrite.length; x++) {
os.write(bWrite[x]); // writes the bytes
}

Example: Write To File Using FileOutputStream Constructor

The following example demonstrates writing to a file using FileOutputStream:

Example


package com.example;

import java.io.*;

public class FileTest {

public static void main(String[] args) {
try {
    byte bWrite[] = {65, 66, 67, 68, 69};
    OutputStream os = new FileOutputStream("output.txt");
    for (int x = 0; x < bWrite.length; x++) {
        os.write(bWrite[x]);
    }
    os.close();
    
    InputStream is = new FileInputStream("output.txt");
    int size = is.available();
    for (int i = 0; i < size; i++) {
        System.out.print((char) is.read() + " ");
    }
    is.close();
} catch (IOException e) {
    System.out.print("Exception");
}
}
}

Output


A B C D E

Write To File Using FileWriter.write() Method

The FileWriter.write() method allows writing characters to a file.

Syntax

Below is a simple example to write data to a file:

Syntax


// Get an existing file
File file = new File("D:/test/testFile1.txt");

// Write content
FileWriter writer = new FileWriter(file);
writer.write("Sample data");
writer.close();

Example: Write To File Using FileWriter.write() Method

The following example demonstrates how to write to a file using FileWriter.write():

Example


package com.example;

import java.io.*;

public class FileTest {

public static void main(String[] args) {
try {
    File file = new File("D:/test/testFile1.txt");

    // Create the file
    if (file.createNewFile()) {
        System.out.println("File is created!");
    } else {
        System.out.println("File already exists.");
    }

    // Write content
    FileWriter writer = new FileWriter(file);
    writer.write("Sample data");
    writer.close();

    // Read content
    FileReader reader = new FileReader(file);
    int c;
    while ((c = reader.read()) != -1) {
        System.out.print((char) c);
    }
} catch (IOException e) {
    System.out.print("Exception");
}
}
}

Output


File is created!
Sample data

Write To File Using Files.write() Method

Files.write() is a newer and more flexible method to create and write to a file in one command.

Syntax

Below is an example to write data to a file using Files.write():

Syntax


String data = "Sample data";
Files.write(Paths.get("D:/test/testFile3.txt"), data.getBytes());

List lines = Arrays.asList("First line", "Second line");
Files.write(Paths.get("file6.txt"), lines, StandardCharsets.UTF_8, 
StandardOpenOption.CREATE, StandardOpenOption.APPEND);

Example: Write To File Using Files.write() Method

The following example demonstrates writing to a file using Files.write():

Example


package com.example;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.util.*;

public class FileTest {

public static void main(String[] args) {
try {
    String data = "Sample data";
    Files.write(Paths.get("D:/test/testFile3.txt"), data.getBytes());

    List lines = Arrays.asList("First line", "Second line");
    Files.write(Paths.get("file6.txt"), lines, StandardCharsets.UTF_8, 
        StandardOpenOption.CREATE, StandardOpenOption.APPEND);

    List content = Files.readAllLines(Paths.get("D:/test/testFile3.txt"));
    System.out.println(content);

    content = Files.readAllLines(Paths.get("file6.txt"));
    System.out.println(content);
} catch (IOException e) {
    System.out.print("Exception");
}
}
}

Output


[Sample data]
[First line, Second line]