Improve `insertInStream`
New version works with infinite streams and has constant space/time complexity.
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@ -2,9 +2,13 @@ package com.baeldung.streams;
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import org.junit.Test;
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import org.junit.Test;
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import java.util.Iterator;
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import java.util.List;
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import java.util.List;
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import java.util.Spliterator;
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import java.util.Spliterators;
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import java.util.stream.Collectors;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import java.util.stream.Stream;
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import java.util.stream.StreamSupport;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertEquals;
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@ -40,6 +44,16 @@ public class StreamAddUnitTest {
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assertEquals(resultList.get(3), (Double) 9.9);
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assertEquals(resultList.get(3), (Double) 9.9);
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}
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}
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private static <T> Stream<T> insertInStream(Stream<T> stream, T elem, int index) {
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final Spliterator<T> spliterator = stream.spliterator();
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final Iterator<T> iterator = Spliterators.iterator(spliterator);
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return Stream.concat(Stream.concat(
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Stream.generate(iterator::next).limit(index),
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Stream.of(elem)),
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StreamSupport.stream(spliterator, /* parallel= */ false));
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}
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private <T> Stream<T> insertInStream(Stream<T> stream, T elem, int index) {
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private <T> Stream<T> insertInStream(Stream<T> stream, T elem, int index) {
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List<T> result = stream.collect(Collectors.toList());
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List<T> result = stream.collect(Collectors.toList());
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result.add(index, elem);
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result.add(index, elem);
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