ppkarwasz commented on code in PR #1411:
URL: https://github.com/apache/commons-lang/pull/1411#discussion_r2203170575
##########
src/main/java/org/apache/commons/lang3/ArrayUtils.java:
##########
@@ -8862,6 +8865,63 @@ public static <T> T[]
toArray(@SuppressWarnings("unchecked") final T... items) {
return items;
}
+ /**
+ * Converts an {@link Iterator} into an array.
+ * <p>
+ * Returns {@code null} if the input iterator is {@code null}.
+ * If the iterator has no elements, an empty {@code Object[]} is returned.
+ * </p>
+ * <p>
+ * Note: The returned array has runtime type {@code Object[]}, and
requires that all elements
+ * in the iterator are of the same type. If a type-safe array is needed,
use
+ * {@link #iteratorToArray(Iterator, Class)} instead.
+ * </p>
+ *
+ * @param iterator the iterator to convert, may be {@code null}
+ * @param <T> the element type
+ * @return the array containing elements from the iterator,
+ * or {@code null} if the input is {@code null}
+ * @since 3.18
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> T[] iteratorToArray(Iterator<T> iterator) {
Review Comment:
This method causes heap pollution: the return type `T[]` can't be created
safely due to type erasure.
The returned type will always be `Object[]`, which will cause a
`ClassCastException` at runtime, when used:
```java
List<String> list = List.of("one", "two", "three");
// Fails at runtime
String[] array = iteratorToArray(list.iterator());
```
##########
src/main/java/org/apache/commons/lang3/ArrayUtils.java:
##########
@@ -8862,6 +8865,63 @@ public static <T> T[]
toArray(@SuppressWarnings("unchecked") final T... items) {
return items;
}
+ /**
+ * Converts an {@link Iterator} into an array.
+ * <p>
+ * Returns {@code null} if the input iterator is {@code null}.
+ * If the iterator has no elements, an empty {@code Object[]} is returned.
+ * </p>
+ * <p>
+ * Note: The returned array has runtime type {@code Object[]}, and
requires that all elements
+ * in the iterator are of the same type. If a type-safe array is needed,
use
+ * {@link #iteratorToArray(Iterator, Class)} instead.
+ * </p>
+ *
+ * @param iterator the iterator to convert, may be {@code null}
+ * @param <T> the element type
+ * @return the array containing elements from the iterator,
+ * or {@code null} if the input is {@code null}
+ * @since 3.18
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> T[] iteratorToArray(Iterator<T> iterator) {
+ if (iterator == null) {
+ return null;
+ }
+
+ if (!iterator.hasNext()) {
+ return (T[]) ArrayUtils.EMPTY_OBJECT_ARRAY;
+ }
+
+ return (T[]) Streams.of(iterator).toArray();
+ }
+
+ /**
+ * Converts an {@link Iterator} into a typed array.
+ * <p>
+ * Returns {@code null} if the input iterator or class is {@code null}.
+ * If the iterator has no elements, an empty array of the specified type
is returned.
+ * </p>
+ *
+ * @param iterator the iterator to convert, may be {@code null}
+ * @param clazz the class of the array component type, must not be
{@code null}
+ * @param <T> the element type
+ * @return the array containing elements from the iterator, or {@code
null} if the input is {@code null}
+ * @since 3.18
+ */
+ @SuppressWarnings("unchecked")
+ public static <T> T[] iteratorToArray(Iterator<T> iterator, Class<T>
clazz) {
+ if (iterator == null || clazz == null) {
+ return null;
+ }
+
+ final List<T> list = new ArrayList<>();
+ iterator.forEachRemaining(list::add);
+
+ final T[] array = (T[]) Array.newInstance(clazz, list.size());
+ return list.toArray(array);
+ }
Review Comment:
Some remarks:
* While returning `null` when the `iterator` is `null` is consistent with
other `ArrayUtils` methods, I would not accept a `null` `Class` argument.
* The method can be safely generalized to accept an `Iterator<? extends T>`
to support subtypes.
* It is not necessary to copy elements into a temporary list first; the
array can be constructed directly via `Stream`.
```suggestion
public static <T> T[] iteratorToArray(Iterator<? extends T> iterator,
Class<T> clazz) {
Objects.requireNonNull(clazz, "clazz must not be null");
return iterator == null
? null
: Streams.of(iterator).toArray(size -> (T[])
Array.newInstance(clazz, size));
}
```
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