File to byte in Java

Question

How do I convert a java.io.File to a byte[]?

Answer 1

It depends on what best means for you. Productivity wise, don't reinvent the wheel and use Apache Commons. 

In Java, we can use Files.readAllBytes(path) to convert a File object into a byte[].

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

  String filePath = "/path/to/file";

  // file to byte[], Path
  byte[] bytes = Files.readAllBytes(Paths.get(filePath));

  // file to byte[], File -> Path
  File file = new File(filePath);
  byte[] bytes = Files.readAllBytes(file.toPath());

Answer 2

Example 1: Convert File to byte[]
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;

public class FileByte {

    public static void main(String[] args) {

        String path = System.getProperty("user.dir") + "\\src\\test.txt";

        try {
            byte[] encoded = Files.readAllBytes(Paths.get(path));
            System.out.println(Arrays.toString(encoded));
        } catch (IOException e) {

        }
    }
}
v

[84, 104, 105, 115, 32, 105, 115, 32, 97, 13, 10, 84, 101, 115, 116, 32, 102, 105, 108, 101, 46]
In the above program, we store the path to the file in the variable path.

Then, inside the try block, we read all the bytes from the given path using readAllBytes() method.