Refactored Stream.flatMap internal iterator to a static class (#2229)

Author: audunhalland

vavr/src/main/java/io/vavr/collection/Stream.java

@@ -1027,25 +1027,7 @@ default Stream<T> filter(Predicate<? super T> predicate) {
  @Override
  default <U> Stream<U> flatMap(Function<? super T, ? extends Iterable<? extends U>> mapper) {
  Objects.requireNonNull(mapper, "mapper is null");
- return isEmpty() ? Empty.instance() : Stream.ofAll(new Iterator<U>() {
-
- final Iterator<? extends T> inputs = Stream.this.iterator();
- java.util.Iterator<? extends U> current = java.util.Collections.emptyIterator();
-
- @Override
- public boolean hasNext() {
- boolean currentHasNext;
- while (!(currentHasNext = current.hasNext()) && inputs.hasNext()) {
- current = mapper.apply(inputs.next()).iterator();
- }
- return currentHasNext;
- }
-
- @Override
- public U next() {
- return current.next();
- }
- });
+ return isEmpty() ? Empty.instance() : Stream.ofAll(new FlatMapIterator<>(this.iterator(), mapper));
  }
 
  @Override
@@ -2100,4 +2082,30 @@ public T getNext() {
  return stream.head();
  }
  }
+
+ final class FlatMapIterator<T, U> implements Iterator<U> {
+
+ final Function<? super T, ? extends Iterable<? extends U>> mapper;
+ final Iterator<? extends T> inputs;
+ java.util.Iterator<? extends U> current = java.util.Collections.emptyIterator();
+
+ FlatMapIterator(Iterator<? extends T> inputs, Function<? super T, ? extends Iterable<? extends U>> mapper) {
+ this.inputs = inputs;
+ this.mapper = mapper;
+ }
+
+ @Override
+ public boolean hasNext() {
+ boolean currentHasNext;
+ while (!(currentHasNext = current.hasNext()) && inputs.hasNext()) {
+ current = mapper.apply(inputs.next()).iterator();
+ }
+ return currentHasNext;
+ }
+
+ @Override
+ public U next() {
+ return current.next();
+ }
+ }
 }