Github user franz1981 commented on a diff in the pull request:
https://github.com/apache/activemq-artemis/pull/2490#discussion_r246323602
--- Diff:
artemis-commons/src/main/java/org/apache/activemq/artemis/utils/collections/MultiIterator.java
---
@@ -0,0 +1,78 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.activemq.artemis.utils.collections;
+
+import java.util.Iterator;
+
+/**
+ * Provides an Iterator that works over multiple underlying iterators.
+ *
+ * @param <T> type of the class of the iterator.
+ */
+public class MultiIterator<T> implements Iterator<T> {
+
+ private final Iterator<T>[] iterators;
+ int index = -1;
+
+ public MultiIterator(Iterator<T>[] iterators) {
+ this.iterators = iterators;
+ }
+
+ @Override
+ public boolean hasNext() {
+ while (true) {
+ if (index != -1) {
+ Iterator<T> currentIterator = get(index);
+ if (currentIterator.hasNext()) {
+ return true;
+ }
+ }
+ int next = index + 1;
+ if (next < iterators.length) {
+ moveTo(next);
+ } else {
+ return false;
+ }
+ }
+ }
+
+ @Override
+ public T next() {
+ while (true) {
+ if (index != -1) {
+ Iterator<T> currentIterator = get(index);
+ if (currentIterator.hasNext()) {
+ return currentIterator.next();
+ }
+ }
+ int next = index + 1;
+ if (next < iterators.length) {
+ moveTo(next);
+ } else {
+ return null;
+ }
+ }
+ }
+
+ protected void moveTo(int index) {
+ this.index = index;
+ }
+
+ protected Iterator<T> get(int index) {
--- End diff --
```java
protected I get(int index)
```
---
