Sometimes there is a need to convert Iterator to Stream to use lambda expression and other functional programming features.

StreamSupport class provides stream(Spliterator spliterator, boolean parallel) method which returns Stream. The second argument in this method is for sequential or parallel stream. We need to provide true for parallel stream.

Iterator does not have any method to return Spliterator instance. So we need to use Spliterators.spliteratorUnknownSize() to get Spliterator.

import java.util.Arrays;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
 
public class IterableToStreamExample 
{
    public static void main(String[] args) 
    {
    	//Iterator to convert to stream
        Iterator<String> iterator = Arrays.asList("a", "b", "c")
                                            .listIterator();
        //Create Spliterator from iterator
        Spliterator<String> splitIterator = Spliterators
                .spliteratorUnknownSize(iterator, Spliterator.ORDERED);
 
        //Use StreamSupport class to get stream from Iterator
        Stream<String> stream = StreamSupport.stream(splitIterator, false);
 
        //Apply Stream operation
        stream.forEach(System.out::println);
    }
}

Output

a
b
c