java 8 Stream - 如何在映射后获取原始对象引用

Question

是否可以使用 Java 8 流来简单地编写以下代码？

代码:-

private double calculateBCMMatrixCostForAnalyte(Long startingMaterialId) {

    double bcmMatrixCost = 0;

    StartingMaterialMatrix smm = startingMaterialMatrixRepository.findByStartingMaterialId(startingMaterialId);

    if (smm.getBlending1MatrixConcentration() != null) {
        bcmMatrixCost += (priceService.findNeatMaterialCostByStartingMaterialId(smm.getBlending1Matrix().getId()) * smm.getBlending1MatrixConcentration()) / 1000000f;
    }

    if (smm.getBlending2MatrixConcentration() != null) {
        bcmMatrixCost += (priceService.findNeatMaterialCostByStartingMaterialId(smm.getBlending2Matrix().getId() * smm.getBlending2MatrixConcentration())) / 1000000f;
    }

    return Precision.round(bcmMatrixCost, 4);
}

我尝试了类似下面的内容

    Stream.of(startingMaterialMatrixRepository.findByStartingMaterialId(startingMaterialId))
            .filter(smm -> smm.getBlending1MatrixConcentration() != null)
            .mapToDouble(smm ->  priceService.findNeatMaterialCostByStartingMaterialId(smm.getStartingMaterial().getId()) * smm.getBlending1MatrixConcentration() / 1000000f);

但在此之后，我将不再有任何对原始“smm”对象的引用来进行进一步检查。

Answer 1

这确实不可读，但在这里

public double streamWay(Long startingMaterialId) {

    return Stream.of(startingMaterialMatrixRepository.findByStartingMaterialId(startingMaterialId))
            .map(Stream::of)
            .flatMapToDouble(smmStream ->
                    DoubleStream.concat(
                            smmStream.filter(smm -> smm.getBlending1MatrixConcentration() != null)
                                    .mapToDouble(smm -> priceService.findNeatMaterialCostByStartingMaterialId(smm.getStartingMaterial().getId()) * smm.getBlending1MatrixConcentration() / 1000000f),
                            smmStream.filter(smm -> smm.getBlending1MatrixConcentration() != null)
                                    .mapToDouble(smm -> priceService.findNeatMaterialCostByStartingMaterialId(smm.getBlending1Matrix().getId() * smm.getBlending2MatrixConcentration()) / 1000000f)
                    )).sum();


}