Simple MD5 Hash Changer made in Java

HashChanger.java

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.security.MessageDigest;
import java.security.SecureRandom;

public class HashChanger {
    private static final SecureRandom random = new SecureRandom();
    private static int filesProcessed;

    public static void main(String[] args) {
        if (args.length == 0) {
            System.out.println("No files were passed, cancelling operation.");
            return;
        }

        for (String file : args) {
            Path p = Paths.get(file);
            String lastHash = fileToMD5(p.toString());
            boolean success = changeMD5(p);

            if (success) {
                String newHash = fileToMD5(p.toString());
                System.out.println(p.getFileName() + " : " + lastHash + " -> " + newHash);
                filesProcessed++;
            }
        }

        if (filesProcessed == 0) {
            System.out.println("No files were hashed.");
        } else {
            System.out.println();
            System.out.println("The hash of " + filesProcessed + " files were changed.");
        }
    }

    private static boolean changeMD5(Path path) {
        try {
            int nullBytes = random.nextInt(5) + 2;
            byte[] bytes = new byte[nullBytes];
            for (int i = 0; i < nullBytes; i++) {
                bytes[i] = (byte) 0;
            }

            Files.write(path, bytes, StandardOpenOption.APPEND);
            return true;
        } catch (IOException e) {
            System.out.println("The file " + path.getFileName().toString() + " failed to undergo MD5 Hash Change.");
            return false;
        }
    }

    public static String fileToMD5(String filePath) {
        try (InputStream inputStream = new FileInputStream(filePath)) {
            byte[] buffer = new byte[1024];
            MessageDigest digest = MessageDigest.getInstance("MD5");
            int numRead = 0;
            while (numRead != -1) {
                numRead = inputStream.read(buffer);
                if (numRead > 0)
                    digest.update(buffer, 0, numRead);
            }
            byte[] md5Bytes = digest.digest();
            return convertHashToString(md5Bytes);
        } catch (Exception e) {
            return null;
        }
    }

    private static String convertHashToString(byte[] md5Bytes) {
        StringBuilder returnVal = new StringBuilder();
        for (byte md5Byte : md5Bytes) {
            returnVal.append(Integer.toString((md5Byte & 0xff) + 0x100, 16).substring(1));
        }
        return returnVal.toString().toUpperCase();
    }
}