How can I convert an Iterator to a Stream without creating unnecessary copies?

Converting an Iterator to a Stream without Copying

Converting an iterator to a stream is useful for leveraging the powerful capabilities of streams without creating unnecessary copies of the original collection. However, avoiding a copy is crucial for performance reasons.

One effective approach is to leverage Java's Spliterator interface. We can create a Spliterator from the iterator, providing a basis for our stream:

<code class="java">Iterator<String> sourceIterator = Arrays.asList("A", "B", "C").iterator();
Stream<String> targetStream = StreamSupport.stream(
          Spliterators.spliteratorUnknownSize(sourceIterator, Spliterator.ORDERED),
          false);</code>

An alternative, which some may find more readable, is to create an Iterable from the iterator using lambdas, since Iterable is a functional interface:

<code class="java">Iterator<String> sourceIterator = Arrays.asList("A", "B", "C").iterator();

Iterable<String> iterable = () -> sourceIterator;
Stream<String> targetStream = StreamSupport.stream(iterable.spliterator(), false);</code>

This method bypasses the need for an intermediate list, ensuring efficient conversion of the iterator to a stream.

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