Java Files readAllBytes()

In this guide, you will learn about the Files readAllBytes() method in Java programming and how to use it with an example.

1. Files readAllBytes() Method Overview


The Files.readAllBytes() method reads all the bytes from a file. The method ensures that the file is closed when all bytes have been read or an I/O error, or other runtime error, occurs.


static byte[] readAllBytes(Path path)


- path: The path to the file.

Key Points:

- This method is intended for reading small files. Large files may lead to an OutOfMemoryError.

- It reads all the content of the file into memory, so it's not suitable for reading very large files.

- The method is useful when you need to quickly read a file's contents without any processing while reading.

2. Files readAllBytes() Method Example

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class ReadAllBytesExample {
    public static void main(String[] args) {
        Path path = Paths.get("sample.txt");

        try {
            byte[] fileBytes = Files.readAllBytes(path);
            String fileContent = new String(fileBytes);
        } catch (IOException e) {
            System.out.println("Error reading the file: " + e.getMessage());


Assuming sample.txt contains:
Hello, World!

The console output will be:
Hello, World!


In this example, Files.readAllBytes() is used to read all the bytes from the file sample.txt. The bytes are then converted into a String for display. 

The method provides a quick way to read the entire content of a file without having to loop through it. However, care should be taken not to use it for very large files as it reads the entire content into memory.