How to Read Data from a BufferedReader into a Byte Array in Java?

How can I read data directly from a BufferedReader into a byte array in Java?

BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
char[] buffer = new char[1024];
int bytesRead = reader.read(buffer);
byte[] byteArray = new byte[bytesRead];
for (int i = 0; i < bytesRead; i++) {
    byteArray[i] = (byte) buffer[i];
}
reader.close();

Reading data from a BufferedReader into a byte array requires converting characters into bytes, as BufferedReader is designed for character streams. This overview provides a detailed approach to achieve this effectively in Java.

// Example of reading from BufferedReader into byte array
import java.io.*;

public class BufferedReaderToByteArray {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
        char[] buffer = new char[1024];
        int bytesRead = reader.read(buffer);

        byte[] byteArray = new byte[bytesRead];
        for (int i = 0; i < bytesRead; i++) {
            byteArray[i] = (byte) buffer[i]; 
        }
        reader.close();

        // Output byte array
        System.out.println(Arrays.toString(byteArray));
    }
}

Causes

• BufferedReader reads text data, not raw byte data.
• bytes and characters are represented differently in Java.

Solutions

• Use the read() method of BufferedReader to read characters into a char array.
• Convert the char array into a byte array manually.

Mistake: Reading directly into a byte array from BufferedReader without conversion.

Solution: Always read into a char array first, then convert to a byte array.

Mistake: Failing to close the BufferedReader after use.

Solution: Use a try-with-resources statement to automatically close the BufferedReader.