code: public static ExchangeRateProvider getExchangeRateProvider(
  			ExchangeRateProviderSupplier provider,
  			ExchangeRateProviderSupplier... providers) {
  
  		List<ExchangeRateProviderSupplier> suppliers = new ArrayList<>();
  		suppliers.add(Objects.requireNonNull(provider));
          suppliers.addAll(Arrays.asList(providers));
  
  		String[] array = suppliers.stream()
  				.map(ExchangeRateProviderSupplier::get).toArray(String[]::new);
  		return getExchangeRateProvider(array);
  
  	}
docs: Access an instance of {@link CurrencyConversion} using the
  {@link ExchangeRateProviderSupplier}.
  
  @param provider
  the exchange rate provider.
  @param providers
  the exchange rate provider.
  @return the exchange rate provider.
  @throws IllegalArgumentException
  if no such {@link ExchangeRateProvider} is available.