java 8 parallel stream问题 [英] java 8 parallel stream Issue

问题描述

    _logger.info("data size : "+saleData.size);

    saleData.parallelStream().forEach(data -> {
                SaleAggrData saleAggrData = new SaleAggrData() {
                    {
                        setCatId(data.getCatId());
                        setRevenue(RoundUpUtil.roundUpDouble(data.getRevenue()));
                        setMargin(RoundUpUtil.roundUpDouble(data.getMargin()));
                        setUnits(data.getUnits());
                        setMarginRate(ComputeUtil.marginRate(data.getRevenue(), data.getMargin()));
                        setOtd(ComputeUtil.OTD(data.getRevenue(), data.getUnits()));
                        setSaleDate(data.getSaleDate());
                        setDiscountDepth(ComputeUtil.discountDepth(data.getRegularPrice(), data.getRevenue()));
                        setTransactions(data.getTransactions());
                        setUpt(ComputeUtil.UPT(data.getUnits(), data.getTransactions()));
                    }
                };
                salesAggrData.addSaleAggrData(saleAggrData);
            });

代码问题是当我从DB获得响应时，以及在使用并行进行迭代时流，每次数据大小都不同，而使用顺序流时它工作正常。

The Issue with code is that when I am getting an response from DB, and while iterating using a parallel stream, the data size is different every time, while when using a sequential stream it's working fine.

我不能使用顺序 Stream 因为数据很大并且花费时间。

I can't use a sequential Stream because the data is huge and it's taking time.

任何线索都会有所帮助。

Any lead would be helpful.

推荐答案

您正在向 salesAggrData 并行添加元素，我假设它是一些集合。如果它不是线程安全的集合，难怪你会得到不一致的结果。

You are adding elements in parallel to salesAggrData which I'm assuming is some Collection. If it's not a thread-safe Collection, no wonder you get inconsistent results.

而不是 forEach ，为什么不使用 map（）然后将结果收集到一些 Collection ？

Instead of forEach, why don't you use map() and then collect the result into some Collection?

List<SaleAggrData> salesAggrData =
    saleData.parallelStream()
            .map(data -> {
                    SaleAggrData saleAggrData = new SaleAggrData() {
                        {
                            setCatId(data.getCatId());
                            setRevenue(RoundUpUtil.roundUpDouble(data.getRevenue()));
                            setMargin(RoundUpUtil.roundUpDouble(data.getMargin()));
                            setUnits(data.getUnits());
                            setMarginRate(ComputeUtil.marginRate(data.getRevenue(), data.getMargin()));
                            setOtd(ComputeUtil.OTD(data.getRevenue(), data.getUnits()));
                            setSaleDate(data.getSaleDate());
                            setDiscountDepth(ComputeUtil.discountDepth(data.getRegularPrice(), data.getRevenue()));
                            setTransactions(data.getTransactions());
                            setUpt(ComputeUtil.UPT(data.getUnits(), data.getTransactions()));
                        }
                    };
                    return saleAggrData;
            })
            .collect(Collectors.toList());

BTW，我可能会更改匿名类实例创建，并使用命名类的构造函数创建 SaleAggrData 实例。

BTW, I'd probably change that anonymous class instance creation, and use a constructor of a named class to create the SaleAggrData instances.

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