There are 2 ways to convert an Iterator to Stream in Java 8 –
- Use
StreamSupport.stream
to convertIterator
into aStream
- Use
StreamSupport.stream
withSpliterator
parameter
1. Iterator to Stream
The Iterator
interface has no spliterator()
method. We need to use Spliterators.spliteratorUnknownSize
to convert the Iterator
into a Spliterator
, followed by StreamSupport.stream
to convert the Spliterator
into a Stream
.
package com.codehelp.java8;
import static java.util.stream.StreamSupport.stream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Collectors;
public class IteratorToStream {
public static void main(final String[] args) {
final List items = new ArrayList<>();
items.add("Alpha");
items.add("Beta");
items.add("Charlie");
items.add("Delta");
items.add("Echo");
items.add("Foxtrot");
final Iterator iterator = items.iterator();
// Iterator -> Spliterators -> Stream -> List
final List result = stream(
Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false)
.map(x -> x.length())
.collect(Collectors.toList());
result.forEach(x -> System.out.println(x));
System.out.println(result.getClass());
}
}
2. Convert Iterator to Stream in Java
Iterable
interface has a spliterator()
method and it is easier to convert it into a Stream
.
package com.codehelp.java8;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
public class IteratorToStream {
public static void main(final String[] args) {
final Iterable iterable = Arrays.asList(1, 2, 3, 4, 5);
// Iterable -> Spliterators -> Stream -> List
final List result = StreamSupport
.stream(
iterable.spliterator(), false)
.map(x -> x * 10)
.collect(Collectors.toList());
result.forEach(x -> System.out.println(x));
System.out.println(result.getClass());
}
}