numerical java8-

• BigDecimal

  • Summing

    BigDecimal  amount = list.stream().map(Order::getAmount).reduce(BigDecimal.ZERO,BigDecimal::add);
    

• List

  • And calculating a property

    //方式一
    int goodsQty = list.stream().mapToInt(OrderDetail::getGoodsSum).sum();
    //方式二
    int goodsQty = list.stream().collect(Collectors.summingInt(OrderDetail::getGoodsSum)).intValue();
    

  • Calculating an attribute of each data packet and after

    Map<String,Integer> goodsSum = list().stream().collect(Collectors.groupingBy(OrderDetail::getGoodsSku,Collectors.summingInt(OrderDetail::getGoodsSum)));
    

  • After calculating the number of each data packet

    Map<String,Long> mobileMap = list.stream().collect(Collectors.groupingBy(Customer::getMobile, Collectors.counting()));
    

  • Obtain a minimum set of attributes object

    BigDecimal minUnitPrice = list.stream().map(GoodsSku::getPrice).min((p1, p2)->p1.compareTo(p2)).get();
    

  • Get the number of a set of attributes

    int GoodsSize=list.stream().collect(Collectors.groupingBy(OrderDetail::getGoodsSku)).size();
    

  • Integrated use (after filtering Conditional Sum)

    allBoxWeight = caseDataList.stream().filter(orderCase->null!=orderCase.getCaseAllPrice()) 
                    .map(SalesOrderCase::getCaseAllWeight).reduce(BigDecimal.ZERO,BigDecimal::add);
    

• summaryStatistics function

  • Function code implementation

    IntSummaryStatistics summaryStatistics = list.stream().mapToInt(Order::getGoodsId).summaryStatistics();
    

  • Gets the number of

    System.out.println("summaryStatistics函数获取数量:"+summaryStatistics.getCount());
    

  • Obtaining an average value

    System.out.println("summaryStatistics函数获取平均值:"+summaryStatistics.getAverage());
    

  • Get the maximum value

     System.out.println("summaryStatistics函数获取最大值:"+summaryStatistics.getMax());
    

  • Get the minimum

    System.out.println("summaryStatistics函数获取最小值:"+summaryStatistics.getMin());
    

  • Summing

    System.out.println("summaryStatistics函数获取和"+summaryStatistics.getSum());