Converting Iterator to Stream Without Copying

Converting an Iterator directly to a Stream without creating an intermediate copy is a desirable operation for performance reasons. Here are two effective methods to achieve this conversion:

Method 1: Using Spliterator

Create a Spliterator from the Iterator using the Spliterators class and use it as the basis for the Stream:

Iterator sourceIterator = Arrays.asList("A", "B", "C").iterator();
Stream targetStream = StreamSupport.stream(
          Spliterators.spliteratorUnknownSize(sourceIterator, Spliterator.ORDERED),
          false);

Method 2: Using Iterable

Create an Iterable from the Iterator using a lambda expression. Iterable is a functional interface, which makes this conversion straightforward:

Iterator sourceIterator = Arrays.asList("A", "B", "C").iterator();

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

The key to avoiding a copy in both methods is that they utilize the StreamSupport class, which allows you to create a Stream directly from a Spliterator or Iterable without intermediate collection manipulation.