code: public static EncryptionUtil getInstance(String key, String salt) throws NoSuchAlgorithmException,
              UnsupportedEncodingException, InvalidKeySpecException {
          if (instance == null) {
              synchronized (EncryptionUtil.class) {
                  if (instance == null) {
                      instance = new EncryptionUtil();
                      generateKeyIfNotAvailable(key, salt);
                  }
              }
          }
          return instance;
      }
docs: Gets the Encryptor.
  
  @param key the key
  @param salt the salt
  @return the Encryptor
  @throws NoSuchAlgorithmException the no such algorithm exception
  @throws UnsupportedEncodingException the unsupported encoding exception
  @throws InvalidKeySpecException the invalid key spec exception