code: public static String encrypt(String secretKey, String plainText) {
          if (plainText == null) {
              return null;
          } else if (plainText.startsWith("$CRYPT::")) {
               // Avoid encrypting already encrypted text - APIMAN-1201
               return plainText;
          }
          
          byte[] encrypted;
          Cipher cipher;
          try {
              SecretKeySpec skeySpec = keySpecFromSecretKey(secretKey);
              
              cipher = Cipher.getInstance("AES"); //$NON-NLS-1$
              cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
          } catch (NoSuchAlgorithmException | NoSuchPaddingException | InvalidKeyException e) {
              throw new RuntimeException(e);
          }
          try {
              encrypted = cipher.doFinal(plainText.getBytes());
          } catch (IllegalBlockSizeException | BadPaddingException e) {
              throw new RuntimeException(e);
          }
          return "$CRYPT::" + new String(Base64.encodeBase64(encrypted)); //$NON-NLS-1$
      }
docs: Encrypt.
  @param plainText the plain text
  @param secretKey the secret key
  @return the string