Encrypt & decrypt Java String

AESCrypto.java

import java.security.Key;
import java.util.Optional;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class AESCrypto {
    
    public Optional<String> encrypt (final String plain, final String secret) {
        Key aesKey = new SecretKeySpec(secret.getBytes(), "AES");

        byte[] encBytes = null;

        try {
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.ENCRYPT_MODE, aesKey);
            encBytes = cipher.doFinal(plain.getBytes());
        } catch (Exception e) {
            return Optional.empty();
        }

        StringBuilder sb = new StringBuilder();
        for (byte b : encBytes) {
            sb.append((char) b);
        }

        return Optional.of(sb.toString());
    }

    public Optional<String> decrypt (final String encrypted, final String secret) {
        Key aesKey = new SecretKeySpec(secret.getBytes(), "AES");

        byte[] bb = new byte[encrypted.length()];
        for (int i = 0; i < encrypted.length(); i++) {
            bb[i] = (byte) encrypted.charAt(i);
        }

        try {
            Cipher cipher = Cipher.getInstance("AES");
            cipher.init(Cipher.DECRYPT_MODE, aesKey);
            return Optional.of(new String(cipher.doFinal(bb)));
        } catch (Exception e) {
            return Optional.empty();
        }
    }

}