java8-Stream流之数值函数（求和、最大值、最小值、平均值）

//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;
    }