code: public boolean isCurrencyAvailable(String code, String... providers) {
          return !getCurrencies(CurrencyQueryBuilder.of().setCurrencyCodes(code).setProviderNames(providers).build())
                  .isEmpty();
      }
docs: Allows to check if a {@link javax.money.CurrencyUnit} instance is defined, i.e.
  accessible from {@link BaseMonetaryCurrenciesSingletonSpi#getCurrency(String, String...)}.
  
  @param code      the currency code, not {@code null}.
  @param providers the (optional) specification of providers to consider. If not set (empty) the providers
  as defined by #getDefaultRoundingProviderChain() should be used.
  @return {@code true} if {@link BaseMonetaryCurrenciesSingletonSpi#getCurrency(String, String...)}
  would return a result for the given code.