Add missing Javadoc to ListenerList

src/changes/changes.xml

@@ -78,6 +78,7 @@ The <action> type attribute can be add,update,fix,remove.
       <action type="fix" dev="ggregory" due-to="Gary Gregory">Fix SpotBugs CT_CONSTRUCTOR_THROW in Base64 by implementing finalize() as a noop to avoid finalizer attacks.</action>
       <action type="fix" dev="ggregory" due-to="Andreas Lemke, Gary Gregory">Increase message limit in IMAPReply.TAGGED_RESPONSE from 80 to 500 characters.</action>
       <action type="fix" dev="ggregory" due-to="Andreas Lemke, Gary Gregory">Increase message limit in IMAPReply.UNTAGGED_RESPONSE from 160 to 500 characters.</action>
+      <action type="fix" dev="ggregory" due-to="Gary Gregory">Add missing Javadoc to ListenerList.</action>
       <!-- ADD -->
       <action type="add" dev="ggregory" due-to="Gary Gregory">org.apache.commons.net.nntp.Article#getChild().</action>
       <action type="add" dev="ggregory" due-to="Gary Gregory">org.apache.commons.net.nntp.Article#getNext().</action>

src/main/java/org/apache/commons/net/util/ListenerList.java

@@ -32,14 +32,27 @@ public class ListenerList implements Serializable, Iterable<EventListener> {
 
     private final CopyOnWriteArrayList<EventListener> listeners;
 
+    /**
+     * Constructs a new instance.
+     */
     public ListenerList() {
         listeners = new CopyOnWriteArrayList<>();
     }
 
+    /**
+     * Adds the given listener to the end of this list.
+     *
+     * @param listener A listener.
+     */
     public void addListener(final EventListener listener) {
         listeners.add(listener);
     }
 
+    /**
+     * Gets the number of elements in this list.
+     *
+     * @return the number of elements in this list
+     */
     public int getListenerCount() {
         return listeners.size();
     }
@@ -60,7 +73,9 @@ private void readObject(final ObjectInputStream ignored) {
     }
 
     /**
-     * Serialization is unnecessary for this class. Reject attempts to do so until such time as the Serializable attribute can be dropped.
+     * Removes the first occurrence of the specified listener from this list, if it is present.
+     *
+     * @param listener listener to be removed from this list, if present.
      */
     public void removeListener(final EventListener listener) {
         listeners.remove(listener);