Add javadoc note to LeafCollector#finish (#12643)
diff --git a/lucene/core/src/java/org/apache/lucene/search/LeafCollector.java b/lucene/core/src/java/org/apache/lucene/search/LeafCollector.java
index ec387ca..2cc9d5c 100644
--- a/lucene/core/src/java/org/apache/lucene/search/LeafCollector.java
+++ b/lucene/core/src/java/org/apache/lucene/search/LeafCollector.java
@@ -125,6 +125,9 @@
* is typically useful to compile data that has been collected on this leaf, e.g. to convert facet
* counts on leaf ordinals to facet counts on global ordinals. The default implementation does
* nothing.
+ *
+ * <p>Note: It can be assumed that this method will only be called once per LeafCollector
+ * instance.
*/
default void finish() throws IOException {}
}