java8-map operation example

• Extracting a set of object properties
  • Print circulation

    list.stream().map(Location::getId).forEach(System.out::println);
    

  • Turn a collection of properties List

    List<String> skus = list.stream().map(Goods::getSku).collect(Collectors.toList());
    

• List turn set

  Set<String> kSet = keys.stream().map(k -> k).collect(Collectors.toSet());
  

• List turn map

  Map<String,InventoryAdjustment>  adjustments = list.stream()
                   .map(InventoryChange::getAdjustment).collect(Collectors.toList())
                   .stream().collect(Collectors.toMap(InventoryAdjustment::getCreatedAt, adjustment->adjustment,(key1, key2)->key1));
  

• List de-duplication (distinct ())

  List<Integer> goodsIds = list.stream().map(OrderDetail::getGoodsId).distinct().collect(Collectors.toList());
  

• Internal operation data

  List<MiddleRedisSkuStock> skuStockList = values.stream().filter(StringUtils::isNotBlank).map(
                      value -> JSON.parseObject(value, MiddleRedisSkuStock.class)
              ).collect(Collectors.toList());
  

• Numeral Calculations
  • BigDecimal sum

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

  • Integert sum

    list.stream().mapToInt(SalesOrderDetail::getGoodsSum).sum();
    

  • Gets a collection of properties minimum

    	BigDecimal minUnitPrice = list.stream().map(GoodsSku::getUnitPrice).min((u1, u2)->u1.compareTo(u2)).get();