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package org.onap.vid.utils;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
public class Streams {
private Streams() {
// hide the implicit public constructor
}
public static <R> Predicate<R> not(Predicate<R> predicate) {
return predicate.negate();
}
public static <T> Stream<T> fromIterator(final Iterator<T> iterator) {
Iterable<T> iterable = () -> iterator;
return StreamSupport.stream(iterable.spliterator(), false);
}
public static <T> Stream<T> fromIterable(final Iterable<T> iterable) {
return StreamSupport.stream(iterable.spliterator(), false);
}
// https://stackoverflow.com/questions/20746429/limit-a-stream-by-a-predicate
private static <T> Spliterator<T> takeWhile(
Spliterator<T> splitr, Predicate<? super T> predicate) {
return new Spliterators.AbstractSpliterator<T>(splitr.estimateSize(), 0) {
boolean stillGoing = true;
@Override public boolean tryAdvance(Consumer<? super T> consumer) {
if (stillGoing) {
boolean hadNext = splitr.tryAdvance(elem -> {
if (predicate.test(elem)) {
consumer.accept(elem);
} else {
stillGoing = false;
}
});
return hadNext && stillGoing;
}
return false;
}
};
}
public static <T> Stream<T> takeWhile(Stream<T> stream, Predicate<? super T> predicate) {
return StreamSupport.stream(takeWhile(stream.spliterator(), predicate), false);
}
}
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