题目：
解法一：
public int getLargestSeriesProduct(String input,int digits) { // put numbers in int array int [] numSet = new int [input.length()]; for (int i = 0; i < numSet.length; i++) { numSet[i] = Character.getNumericValue(input.charAt(i)); } // calculate the largest series product int largestProduct = 0; int sum = 1; for (int i = 0; i < (numSet.length - digits); i++) { for (int j = 0; j < digits; j++) { if (numSet[i + j] == 0) {sum = 0;break;} sum *= numSet[i + j]; } if (sum > largestProduct) {largestProduct = sum;} sum = 1; } return largestProduct; }解法二：
import io.vavr.collection.Stream; import io.vavr.collection.Traversable; import java.util.regex.Pattern; public class LargestSeriesProductCalculator { private final String numbers; public LargestSeriesProductCalculator(String numbers) { if (numbers == null) { throw new IllegalArgumentException("String to search must be non-null."); } if (Pattern.compile("[^0-9]").matcher(numbers).find()) { throw new IllegalArgumentException("String to search may only contains digits."); } this.numbers = numbers; } public long calculateLargestProductForSeriesLength(int window) { if (window < 0) { throw new IllegalArgumentException("Series length must be non-negative."); } if (window == 0) { return 1; } if (window > numbers.length()) { throw new IllegalArgumentException("Series length must be less than or equal to the length of the string to search."); } return Stream.ofAll(numbers.toCharArray()) .map(Character::getNumericValue) .sliding(window) .map(Traversable::product) .max() .getOrElseThrow(() -> new ArithmeticException("No maximum found in sequence")) .longValue(); } }