d setValue(String value) {
      this.value = value;
    }
  }

  /**
   * Checks if an address is valid. A valid address consists of a number
   * followed by a street name, which may be composed of multiple words.
   *
   * @param address the address
   * @return true if valid, false if invalid
   */
  public static boolean isAddressValid(String address) {
    // Cannot be null.
    if (address == null) {
      return false;
    }

    // Must have two or more parts.
    String[] parts = address.split(" "