JAVA8问题处理回顾-持续更新
金额累加问题 使用Reduce进行累加操作，参考这里 List<BigDecimal> bdList = new ArrayList<>(); //populate list BigDecimal result = bdList.stream().reduce(BigDecimal.ZERO, BigDecimal::add); 查找集合的最后一个元素 JAVA8的Stream只提供了FindFirst功能，没有FindLast功能，可以使用Reduce来实现查找最后一个元素的效果 import java.util.*; import java.util.stream.*; public class GetLastEleFromCollection { public static void main(String[] args) { List<String> list = new ArrayList<>(); list.add("aaa"); list.add("idddd"); list.add("bbbb"); String lastElement = list.stream() .reduce((first, second) -> second) .orElse(null); System.out.println(lastElement); } } bbbb 比较两个时间是否是同一天 import java.time.*; import java.time.temporal.*; public class CompareDay { public static void main(String[] args) { final LocalDateTime now = LocalDateTime.now(); final LocalDateTime localDateTime = LocalDateTime.of(2019, 9, 29, 0, 0, 0); System.out.println(localDateTime.truncatedTo(ChronoUnit.DAYS).isEqual(now.truncatedTo(ChronoUnit.DAYS))); } } true 实现与Python的zip函数功能 import java.util.*; import java.util.function.*; public class Zip { public static void main(String[] args) { List<List<Integer>> result = handle(Arrays.asList(1, 2, 3), Arrays.asList(4, 5, 6), (i, j) -> Arrays.asList(i, j)); System.out.println(result); } public static <T, U, R> List<R> handle(List<T> list, List<U> list1, BiFunction<T, U, R> biFunction) { List<R> result = new ArrayList<>(); for(int i = 0; i < list.size(); i ++) { result.add(biFunction.apply(list.get(i), list1.get(i))); } return result; } } [[1 (\, 4)] (\, [2 (\, 5)]) (\, [3 (\, 6)])] 多个Predicate链 import java.util.*; import java.util.stream.*; import java.util.function.*; public class MorePredicate { public static void main(String[] args) { List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6); final Predicate<Integer> predicate = i -> i % 2 == 0; final Predicate<Integer> predicate1 = predicate.and(integer -> integer > 5); List<Integer> result = list.stream() .filter(predicate1) .collect(Collectors.toList()); System.out.println(result); } } [6]