code: public synchronized String encrypt(String plainText) {
          assertArgumentNotNull("plainText", plainText);
          if (encryptingCipher == null) {
              initialize();
          }
          return new String(encodeHex(doEncrypt(plainText)));
      }
docs: Encrypt the text as invertible.
  @param plainText The plain text to be encrypted. (NotNull, EmptyAllowed)
  @return The encrypted text from the plain text. (NotNull, EmptyAllowed: depends on algorithm)
  @throws CipherFailureException When the cipher fails.