Java lambda 循环累加求和_angus_Lucky的博客-CSDN博客_lambda求和

安宇雨 - 随手采集
2020-06-17 22:14:04
随手采集
0000-未整理-等待研究

java 8 stream 提供了下面几种类型的求和

Stream::mapToInt
Stream::mapToDouble
Stream::mapToLong

     public void test() {        List<Person> people = new ArrayList<>();        people.add(new Person("zhangsan",20));        people.add(new Person("lisi", 26));        people.add(new Person("wangwu",35));                int sum = people.stream()                  .mapToInt(p -> p.getAge())                  .sum();        System.out.println("Total of ages " + sum);    }

但是没有BigDecimal类型，可以使用下面方法实现

    public void test() {        List<Person> list = new ArrayList<>();        list.add(new Person("zhangsan", 20, new BigDecimal(10.5)));        list.add(new Person("lisi", 26, new BigDecimal(22.2)));        list.add(new Person("wangwu", 35, new BigDecimal(15.54)));         BigDecimal amounts = list.stream().map(item -> item.getAmount())                .reduce(BigDecimal.ZERO, BigDecimal::add);        amounts = amounts.setScale(1, BigDecimal.ROUND_DOWN);        System.out.println("Total of amounts:" + amounts);         // 或者        BigDecimal sum = list                .stream()                .map(Person::getAmount)                .reduce(BigDecimal::add)                .get();        sum = sum.setScale(1, BigDecimal.ROUND_DOWN);        System.out.println("Total of sums: " + sum);    }

Original url: Access
Created at: 2020-06-17 22:14:02
Category: default
Tags: none

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