Is there a Java 8 stream operation that limits a (potentially infinite) Stream
until the first element fails to match a predicate?
In Java 9 we can use
Here is a version done on ints - as asked in the question.
Usage:
StreamUtil.takeWhile(IntStream.iterate(1, n -> n + 1), n -> n < 10);
Here's code for StreamUtil:
import java.util.PrimitiveIterator;
import java.util.Spliterators;
import java.util.function.IntConsumer;
import java.util.function.IntPredicate;
import java.util.stream.IntStream;
import java.util.stream.StreamSupport;
public class StreamUtil
{
public static IntStream takeWhile(IntStream stream, IntPredicate predicate)
{
return StreamSupport.intStream(new PredicateIntSpliterator(stream, predicate), false);
}
private static class PredicateIntSpliterator extends Spliterators.AbstractIntSpliterator
{
private final PrimitiveIterator.OfInt iterator;
private final IntPredicate predicate;
public PredicateIntSpliterator(IntStream stream, IntPredicate predicate)
{
super(Long.MAX_VALUE, IMMUTABLE);
this.iterator = stream.iterator();
this.predicate = predicate;
}
@Override
public boolean tryAdvance(IntConsumer action)
{
if (iterator.hasNext()) {
int value = iterator.nextInt();
if (predicate.test(value)) {
action.accept(value);
return true;
}
}
return false;
}
}
}