Stream常用操作

 

一 、list 加法

BigDecimal 类型:
BigDecimal bb =list.stream().map(Plan::getAmount).reduce(BigDecimal.ZERO,BigDecimal::add);
 

int、double、long 类型:

double max = list.stream().mapToDouble(User::getHeight).sum();

二、合并list

 public static void main(String[] args) throws InterruptedException, ExecutionException {
        List<Integer> listA = Arrays.asList(new Integer[]{1, 2});
        List<Integer> listB = Arrays.asList(new Integer[]{3, 4});
        List<Integer> res = Stream.of(listA, listB).flatMap(Collection::stream).collect(Collectors.toList());
        System.out.println(res.size());
        res.forEach(System.out::println);
}

三、将list中对象属性取出放到另一个list

list result = list.stream().map(Student:: getName).collect(collectors.tolist());