JavaStream流之求和的实现

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

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

//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 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 createSalesOrder(){
  List 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;
 }