Dónal :
Given a list of prices, I want to find the index of the the largest price that exceeds a certain minimum. My current solution looks like this:
public class Price {
public static Integer maxPriceIndex(List<Integer> prices, Integer minPrice) {
OptionalInt maxPriceIndexResult = IntStream.range(0, prices.size())
.reduce((a, b) -> prices.get(a) > prices.get(b) ? a : b);
if (maxPriceIndexResult.isPresent()) {
int maxPriceIndex = maxPriceIndexResult.getAsInt();
int maxFuturePrice = prices.get(maxPriceIndex);
if (maxFuturePrice > minPrice) {
return maxPriceIndex;
}
}
return null;
}
public static void main(String[] args) {
List<Integer> prices = Arrays.asList(5, 3, 2);
Integer result = maxPriceIndex(prices, 6);
System.out.println("Final result: " + result);
}
}
I don't like this mix of imperative and functional code, but can't figure out a way of changing the reducer so that it also compares the price with minPrice. Is there a purely functional solution to this problem?
MikeFHay :
You can do the filter before finding the max.
IntStream.range(0, prices.size())
.filter(i -> prices.get(i) > minPrice)
.reduce((a, b) -> prices.get(a) > prices.get(b) ? a : b);
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