Adding Bigdecimals inside java 8 stream

问题

I would like to know if one way is more effecient than the other. Is there a better java 8 way to do the following operation ?

java 8 way

BigDecimal total = entries.parallelStream()
    .map(poec -> BigDecimal.valueOf(poec.getQuantity().longValue() * poec.getAdjustedUnitPrice().doubleValue()))
    .collect(Collectors.toList()).stream()
    .reduce(BigDecimal.ZERO, BigDecimal::add);

Normal Java 7 way

    for (final EntryConsumed poec : entries) {
      total = total.add(BigDecimal.valueOf(poec.getQuantity().longValue() * poec.getAdjustedUnitPrice().doubleValue()));
    }

回答1:

You have some redundant code in your Java 8 solution. It can be simplified to:

BigDecimal total = entries.parallelStream()
            .map(poec -> BigDecimal.valueOf(poec.getQuantity().longValue() * poec.getAdjustedUnitPrice().doubleValue()))
            .reduce(BigDecimal.ZERO, BigDecimal::add);

As for performance, you can calculate this yourself by benchmarking the two solutions.

来源：https://stackoverflow.com/questions/37659181/adding-bigdecimals-inside-java-8-stream