BigDecimal bb =list.stream().map(Plan::getAmount).reduce(BigDecimal.ZERO,BigDecimal::add);int、double、long:

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

補(bǔ)充：java8-Stream流之?dāng)?shù)值函數(shù)（求和、最大值、最小值、平均值）

我就廢話不多說了，大家還是直接看代碼吧~

//todo stream流的使用 //todo filter：過濾操作；保留符合過濾條件的對(duì)象；這是一個(gè)中間操作；后面可以帶最終操作 //todo mapToInt: 將數(shù)據(jù)根據(jù)double類型來處理； public static void main(String[] args) { List<SalesOrder> list = createSalesOrder(); //獲取集合中城市為上海的數(shù)量 System.out.println('mapToInt獲取和:'+list.stream().filter(s -> s.getConsigneeCity().equals('上海')) .mapToInt(SalesOrder::getCreateUserId).sum()); //利用stream流中的函數(shù)獲取相關(guān)數(shù)值信息 IntSummaryStatistics summaryStatistics = list.stream().filter(s -> s.getConsigneeCity().equals('上海')) .mapToInt(SalesOrder::getCreateUserId).summaryStatistics(); System.out.println('summaryStatistics函數(shù)獲取數(shù)量:'+summaryStatistics.getCount()); System.out.println('summaryStatistics函數(shù)獲取平均值:'+summaryStatistics.getAverage()); System.out.println('summaryStatistics函數(shù)獲取最大值:'+summaryStatistics.getMax()); System.out.println('summaryStatistics函數(shù)獲取最小值:'+summaryStatistics.getMin()); System.out.println('summaryStatistics函數(shù)獲取和'+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('廣州'); salesOrder.setCreateUserId(30); list.add(salesOrder); salesOrder = new SalesOrder(); salesOrder.setConsigneeCity('杭州'); salesOrder.setCreateUserId(40); list.add(salesOrder); return list; }

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持好吧啦網(wǎng)。如有錯(cuò)誤或未考慮完全的地方，望不吝賜教。