Created
November 14, 2018 20:12
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Interleave two streams of the same type in Java 8
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Stream<String> a = Stream.of("one", "three", "five"); | |
Stream<String> b = Stream.of("two", "four", "six"); | |
Stream<String> out = interleave(a, b); | |
/** | |
* https://stackoverflow.com/questions/53307682/how-to-interleave-merge-two-java-8-streams | |
**/ | |
public static <T> Stream<T> interleave(Stream<T> streamA, Stream<T> streamB) { | |
return zip(streamA, streamB, (o1, o2) -> Stream.of(o1, o2)).flatMap(s -> s); | |
} | |
/** | |
* https://stackoverflow.com/questions/17640754/zipping-streams-using-jdk8-with-lambda-java-util-stream-streams-zip | |
**/ | |
private static <A, B, C> Stream<C> zip(Stream<A> streamA, Stream<B> streamB, BiFunction<A, B, C> zipper) { | |
final Iterator<A> iteratorA = streamA.iterator(); | |
final Iterator<B> iteratorB = streamB.iterator(); | |
final Iterator<C> iteratorC = new Iterator<C>() { | |
@Override | |
public boolean hasNext() { | |
return iteratorA.hasNext() && iteratorB.hasNext(); | |
} | |
@Override | |
public C next() { | |
return zipper.apply(iteratorA.next(), iteratorB.next()); | |
} | |
}; | |
final boolean parallel = streamA.isParallel() || streamB.isParallel(); | |
return iteratorToFiniteStream(iteratorC, parallel); | |
} | |
private static <T> Stream<T> iteratorToFiniteStream(Iterator<T> iterator, boolean parallel) { | |
final Iterable<T> iterable = () -> iterator; | |
return StreamSupport.stream(iterable.spliterator(), parallel); | |
} |
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