Improve readability of empty collection checks

ldap/src/test/java/org/apache/directory/server/core/avltree/ArrayMarshaller.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,7 +73,7 @@ public class ArrayMarshaller<E> implements Marshaller<ArrayTree<E>> {
 	 * @param tree the tree to be marshalled
 	 */
 	public byte[] serialize(ArrayTree<E> tree) {
-		if ((tree == null) || (tree.size() == 0)) {
+		if ((tree == null) || tree.isEmpty()) {
 			return EMPTY_TREE;
 		}