Encrypt a BMP image

import java.io.File;
import java.io.RandomAccessFile;
import java.io.IOException;

public class EncryptBMPImage {
    public static void main(String[] args) {
        String fileName = "logo.bmp";

        try (RandomAccessFile file = new RandomAccessFile(fileName, "rw")) {
            // Check if it's a valid BMP file
            char b1 = (char) file.read();
            char b2 = (char) file.read();
            
            if (b1 == 'B' && b2 == 'M') {
                // If it's a valid BMP, encrypt it by changing the header
                file.seek(0);
                file.write((byte) 'M');
                file.write((byte) 'P');
                System.out.println("Image encrypted successfully.");
            } else {
                System.out.println("Not a valid BMP file.");
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}