FileEncryptor.java

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.SecretKey;
import java.io.*;

public class FileEncryptor {
    public static void encryptFile(String inputFile, String outputFile, SecretKey key) throws Exception {
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, key);

        try (FileInputStream fis = new FileInputStream(inputFile);
             FileOutputStream fos = new FileOutputStream(outputFile);
             CipherOutputStream cos = new CipherOutputStream(fos, cipher)) {

            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = fis.read(buffer)) != -1) {
                cos.write(buffer, 0, bytesRead);
            }
        }
        System.out.println("Encryption successful! Encrypted file saved as " + outputFile);
    }
}