List constructor arg initialized correctly

DataBinder now uses the calculated List size rather than
the number of indexes to initialize the list.

Closes gh-34145

Author: rstoyanchev

spring-context/src/main/java/org/springframework/validation/DataBinder.java

@@ -1060,7 +1060,9 @@ private <V> List<V> createList(
 		}
 		int size = (indexes.last() < this.autoGrowCollectionLimit ? indexes.last() + 1 : 0);
 		List<V> list = (List<V>) CollectionFactory.createCollection(paramType, size);
-		indexes.forEach(i -> list.add(null));
+		for (int i = 0; i < size; i++) {
+			list.add(null);
+		}
 		for (int index : indexes) {
 			list.set(index, (V) createObject(elementType, paramPath + "[" + index + "].", valueResolver));
 		}

spring-context/src/test/java/org/springframework/validation/DataBinderConstructTests.java

@@ -121,6 +121,24 @@ void listBinding() {
 		assertThat(list.get(2).param1()).isEqualTo("value3");
 	}
 
+	@Test // gh-34145
+	void listBindingWithNonconsecutiveIndices() {
+		MapValueResolver valueResolver = new MapValueResolver(Map.of(
+				"dataClassList[0].param1", "value1", "dataClassList[0].param2", "true",
+				"dataClassList[1].param1", "value2", "dataClassList[1].param2", "true",
+				"dataClassList[3].param1", "value3", "dataClassList[3].param2", "true"));
+
+		DataBinder binder = initDataBinder(ListDataClass.class);
+		binder.construct(valueResolver);
+
+		ListDataClass dataClass = getTarget(binder);
+		List<DataClass> list = dataClass.dataClassList();
+
+		assertThat(list.get(0).param1()).isEqualTo("value1");
+		assertThat(list.get(1).param1()).isEqualTo("value2");
+		assertThat(list.get(3).param1()).isEqualTo("value3");
+	}
+
 	@Test
 	void mapBinding() {
 		MapValueResolver valueResolver = new MapValueResolver(Map.of(