java Convert an Iterator to Iterable in Java

 

参考资料： https://www.techiedelight.com/convert-iterator-iterable-java/

1. Java 7 and before

import java.util.Arrays;
import java.util.Iterator;

// Program to Convert an Iterator to Iterable in Java
class IteratorUtils
{
	public static<T> Iterable<T> iteratorToIterable(Iterator<T> iterator) {
		return new Iterable<T>() {
			@Override
			public Iterator<T> iterator() {
				return iterator;
			}
		};
	}

	public static void main(String[] args)
	{
		Iterator<Integer> iterator = Arrays.asList(1, 2, 3, 4, 5).iterator();

		Iterable<Integer> iterable = iteratorToIterable(iterator);
		iterable.forEach(System.out::println);
	}
}

 

 

2. Java 8 and above

import java.util.Arrays;
import java.util.Iterator;

// Program to Convert an Iterator to Iterable in Java 8 and above
class IteratorUtils
{
	public static<T> Iterable<T> iteratorToIterable(Iterator<T> iterator) {
		return () -> iterator;
	}

	public static void main(String[] args)
	{
		Iterator<Integer> iterator = Arrays.asList(1, 2, 3, 4, 5).iterator();

		Iterable<Integer> iterable = iteratorToIterable(iterator);
		iterable.forEach(System.out::println);
	}
}

 

3. Converting Iterator to Spliterators

import java.util.Arrays;
import java.util.Iterator;
import java.util.Spliterators;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

// Program to Convert an Iterator to Iterable in Java
class IteratorUtils
{
	private static <T> Iterable<T> iteratorToIterable(Iterator<T> iterator)
	{
		// 1. Convert the iterator into a Spliterator
		// 2. Convert the spliterator into a sequential stream
		// 3. Convert the stream to an iterable
		return StreamSupport
					.stream(Spliterators.spliteratorUnknownSize(iterator, 0),
							false)
					.collect(Collectors.toList());
	}

	public static void main(String[] args)
	{
		Iterator<Integer> iterator = Arrays.asList(1, 2, 3, 4, 5).iterator();

		Iterable<Integer> iterable = iteratorToIterable(iterator);
		iterable.forEach(System.out::println);
	}
}