链接Java可选地图和orElse(if-else-style) [英] Chaining of Java Optional map and orElse (if-else-style)
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问题描述
在Java中是否有优雅的流媒体方式说如果值存在,则将此可选映射到具有计算值的另一个可选,否则返回空可选?
<我想到了类似的东西:
可选< Float>金额= ...;
可选< MonetaryAmount> myAmount = amount
.map(theAmount - > FastMoney.of(theAmount,EUR))。orElse(Optional.empty());
但这是不可能的。
我提出的解决方案有点冗长而且不像流媒体一样:
可选< Float>金额= ...;
可选< MonetaryAmount> myAmount = amount.isPresent()?
Optional.of(FastMoney.of(amount.get(),EUR)):Optional.empty();
解决方案
您不需要 orElse
子句:
可选< Float>金额= ...;
可选< MonetaryAmount> myAmount =
amount.map(theAmount - > FastMoney.of(theAmount,EUR));
Is there an elegant and streaming way in Java to say "map this Optional to another Optional with a computed value if the value exists, else return an empty Optional"?
I thought of something like:
Optional<Float> amount = ...;
Optional<MonetaryAmount> myAmount = amount
.map(theAmount -> FastMoney.of(theAmount, "EUR")).orElse(Optional.empty());
But this is not possible.
The solution I came up with is somewhat verbose and not streaming-like:
Optional<Float> amount = ...;
Optional<MonetaryAmount> myAmount = amount.isPresent() ?
Optional.of(FastMoney.of(amount.get(), "EUR")) : Optional.empty();
解决方案
You don't need the orElse
clause:
Optional<Float> amount = ...;
Optional<MonetaryAmount> myAmount =
amount.map(theAmount -> FastMoney.of(theAmount, "EUR"));
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