Java 8 根据条件应用流过滤器
在 Java 8 中，有没有办法根据条件在流上应用过滤器，
In Java 8, is there a way to apply the filter on a stream based on a condition,
例子
我有这个直播
if (isAccessDisplayEnabled) {
src = (List < Source > ) sourceMeta.getAllSources.parallelStream()
.filter(k - > isAccessDisplayEnabled((Source) k))
.filter(k - > containsAll((Source) k, substrings, searchString))
.collect(Collectors.toList());
} else {
src = (List < Source > ) sourceMeta.getAllSources.parallelStream()
.filter(k - > containsAll((Source) k, substrings, searchString))
.collect(Collectors.toList());
}
我正在添加过滤器
.filter(k - > isAccessDisplayEnabled((Source) k)))
基于 if-else 条件的流.有没有办法避免 if-else，因为如果有更多的过滤器出现，那么它将很难维护.
on the stream based on the if-else condition. Is there a way to avoid that if-else, since if there are more filters coming up,then it will be hard to maintain.
请告诉我
推荐答案
一种方法是
Stream<Source> stream = sourceMeta.getAllSources.parallelStream().map(x -> (Source)x);
if(isAccessDisplayEnabled) stream = stream.filter(s -> isAccessDisplayEnabled(s));
src = stream.filter(s - > containsAll(s, substrings, searchString))
.collect(Collectors.toList());
另一个
src = sourceMeta.getAllSources.parallelStream().map(x -> (Source)x)
.filter(isAccessDisplayEnabled? s - > isAccessDisplayEnabled(s): s -> true)
.filter(s - > containsAll(s, substrings, searchString))
.collect(Collectors.toList());
在任何一种情况下，请注意在开头执行一种类型转换如何简化整个流管道.
In either case, note how performing one type cast at the beginning simplifies the entire stream pipline.
这两种解决方案都避免为每个流元素重新评估 isAccessDisplayEnabled，但是，第二种方法依赖于 JVM 内联 s -> 的能力.当此代码对性能至关重要时，为 true.
Both solutions avoid re-evaluating isAccessDisplayEnabled for every stream element, however, the second relies on the JVM’s capability of inlining s -> true when this code turns out to be performance critical.
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