java stream流的高级使用

//orderStockoutDetails中的每一项的getOrderDetailId对应的名称
Map skuNameMap = orderStockoutDetails.stream().collect(Collectors.toMap(OrderStockoutDetail::getOrderDetailId, OrderStockoutDetail::getSkuName, (i1, i2) -> i2));


//orderStockoutDetails中的每一项的getOrderDetailId对应的数量
Map skuAmount = orderStockoutDetails.stream().collect(Collectors.groupingBy(OrderStockoutDetail::getOrderDetailId, Collectors.summingInt(OrderStockoutDetail::getAmount)));

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//allItem中的每一项的getOrderDetailId对应的数量
Map skuAmount2 = allItem.stream().collect(Collectors.groupingBy(ShipItemDTO::getOrderDetailId, Collectors.summingInt(ShipItemDTO::getAmount)));