Java Files readAllBytes()

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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

Definition:

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.

Syntax:

static byte[] readAllBytes(Path path)

Parameters:

- 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.io.IOException;
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);
            System.out.println(fileContent);
        } catch (IOException e) {
            System.out.println("Error reading the file: " + e.getMessage());
        }
    }
}

Output:

Assuming sample.txt contains:
Hello, World!

The console output will be:
Hello, World!

Explanation:

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.