BigDecimal:
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BigDecimal bb =list.stream().map(Plan::getAmount).reduce(BigDecimal.ZERO,BigDecimal::add); |
int、double、long:
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double max = list.stream().mapToDouble(User::getHeight).sum(); |
补充:java8-Stream流之数值函数(求和、最大值、最小值、平均值)
我就废话不多说了,大家还是直接看代码吧~
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//todo stream流的使用 //todo filter:过滤操作;保留符合过滤条件的对象;这是一个中间操作;后面可以带最终操作 //todo mapToInt: 将数据根据double类型来处理; public static void main(String[] args) { List<SalesOrder> list = createSalesOrder(); //获取集合中城市为上海的数量 System.out.println( "mapToInt获取和:" +list.stream().filter(s -> s.getConsigneeCity().equals( "上海" )) .mapToInt(SalesOrder::getCreateUserId).sum()); //利用stream流中的函数获取相关数值信息 IntSummaryStatistics summaryStatistics = list.stream().filter(s -> s.getConsigneeCity().equals( "上海" )) .mapToInt(SalesOrder::getCreateUserId).summaryStatistics(); System.out.println( "summaryStatistics函数获取数量:" +summaryStatistics.getCount()); System.out.println( "summaryStatistics函数获取平均值:" +summaryStatistics.getAverage()); System.out.println( "summaryStatistics函数获取最大值:" +summaryStatistics.getMax()); System.out.println( "summaryStatistics函数获取最小值:" +summaryStatistics.getMin()); System.out.println( "summaryStatistics函数获取和" +summaryStatistics.getSum()); } static List<SalesOrder> createSalesOrder(){ List<SalesOrder> list = new LinkedList<>(); SalesOrder salesOrder = new SalesOrder(); salesOrder.setCreateUserId( 12 ); salesOrder.setConsigneeCity( "上海" ); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity( "上海" ); salesOrder.setCreateUserId( 24 ); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity( "北京" ); salesOrder.setCreateUserId( 18 ); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity( "深圳" ); salesOrder.setCreateUserId( 16 ); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity( "广州" ); salesOrder.setCreateUserId( 30 ); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity( "杭州" ); salesOrder.setCreateUserId( 40 ); list.add(salesOrder); return list; } |
以上为个人经验,希望能给大家一个参考,也希望大家多多支持服务器之家。如有错误或未考虑完全的地方,望不吝赐教。
原文链接:https://invincible.blog.csdn.net/article/details/95994908