tkalkirill commented on a change in pull request #589:
URL: https://github.com/apache/ignite-3/pull/589#discussion_r793496628
##########
File path:
modules/core/src/main/java/org/apache/ignite/internal/util/CollectionUtils.java
##########
@@ -197,13 +202,100 @@ public T next() {
};
}
+ /**
+ * Create a lazy concatenation of iterators.
+ *
+ * <p>NOTE: {@link Iterator#remove} - not supported.
+ *
+ * @param iterators Iterators.
+ * @param <T> Type of the elements.
+ * @return Concatenation of iterators.
+ */
+ @SafeVarargs
+ public static <T> Iterator<T> concat(@Nullable Iterator<? extends T>...
iterators) {
Review comment:
I wrote above about the impossibility of using streams now.
##########
File path:
modules/core/src/main/java/org/apache/ignite/internal/util/CollectionUtils.java
##########
@@ -197,13 +202,100 @@ public T next() {
};
}
+ /**
+ * Create a lazy concatenation of iterators.
+ *
+ * <p>NOTE: {@link Iterator#remove} - not supported.
+ *
+ * @param iterators Iterators.
+ * @param <T> Type of the elements.
+ * @return Concatenation of iterators.
+ */
+ @SafeVarargs
+ public static <T> Iterator<T> concat(@Nullable Iterator<? extends T>...
iterators) {
+ if (iterators == null || iterators.length == 0) {
+ return emptyIterator();
+ }
+
+ return new Iterator<>() {
+ /** Current index at {@code iterators}. */
+ int idx = 0;
+
+ /** Current iterator. */
+ Iterator<? extends T> curr = emptyIterator();
+
+ /** {@inheritDoc} */
+ @Override
+ public boolean hasNext() {
+ while (!curr.hasNext() && idx < iterators.length) {
+ curr = iterators[idx++];
+ }
+
+ return curr.hasNext();
+ }
+
+ /** {@inheritDoc} */
+ @Override
+ public T next() {
+ if (!hasNext()) {
+ throw new NoSuchElementException();
+ } else {
+ return curr.next();
+ }
+ }
+ };
+ }
+
+ /**
+ * Create a lazy concatenation of iterators.
+ *
+ * <p>NOTE: {@link Iterator#remove} - not supported.
+ *
+ * @param iterators Iterators.
+ * @param <T> Type of the elements.
+ * @return Concatenation of iterators.
+ */
+ public static <T> Iterator<T> concat(@Nullable Collection<Iterator<?
extends T>> iterators) {
Review comment:
I wrote above about the impossibility of using streams now.
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