Fix SpotBugs errors

[ERROR] Medium:
org.apache.commons.io.monitor.FileAlterationMonitor.getObservers() may
expose internal representation by returning
FileAlterationMonitor.observers [org.apache.commons.io.monitor.FileAlterationMonitor]
At FileAlterationMonitor.java:[line 124] EI_EXPOSE_REP
[ERROR] Medium:
org.apache.commons.io.monitor.FileAlterationObserver.getListeners() may
expose internal representation by returning
FileAlterationObserver.listeners [org.apache.commons.io.monitor.FileAlterationObserver]
At FileAlterationObserver.java:[line 397] EI_EXPOSE_REP

Author: garydgregory

src/changes/changes.xml

@@ -59,6 +59,7 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: Class org.apache.commons.io.filefilter.DelegateFileFilter defines non-transient non-serializable instance field fileFilter [org.apache.commons.io.filefilter.DelegateFileFilter] In DelegateFileFilter.java SE_BAD_FIELD.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: Class org.apache.commons.io.filefilter.DelegateFileFilter defines non-transient non-serializable instance field fileNameFilter [org.apache.commons.io.filefilter.DelegateFileFilter] In DelegateFileFilter.java SE_BAD_FIELD.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.function.IOStream$1.next() cannot throw NoSuchElementException [org.apache.commons.io.function.IOStream$1] At IOStream.java:[line 98] IT_NO_SUCH_ELEMENT.</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.monitor.FileAlterationMonitor.getObservers() may expose internal representation by returning FileAlterationMonitor.observers [org.apache.commons.io.monitor.FileAlterationMonitor] At FileAlterationMonitor.java:[line 124] EI_EXPOSE_REP.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: Class org.apache.commons.io.monitor.FileAlterationObserver defines non-transient non-serializable instance field fileFilter [org.apache.commons.io.monitor.FileAlterationObserver] In FileAlterationObserver.java SE_BAD_FIELD.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: Class org.apache.commons.io.monitor.FileAlterationObserver defines non-transient non-serializable instance field listeners [org.apache.commons.io.monitor.FileAlterationObserver] In FileAlterationObserver.java SE_BAD_FIELD.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.FileCleaningTracker.getDeleteFailures() may expose internal representation by returning FileCleaningTracker.deleteFailures [org.apache.commons.io.FileCleaningTracker] At FileCleaningTracker.java:[line 218] EI_EXPOSE_REP.</action>

src/main/java/org/apache/commons/io/monitor/FileAlterationMonitor.java

@@ -17,6 +17,7 @@
 package org.apache.commons.io.monitor;
 
 import java.time.Duration;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -121,7 +122,7 @@ public long getInterval() {
      * @return The set of {@link FileAlterationObserver}
      */
     public Iterable<FileAlterationObserver> getObservers() {
-        return observers;
+        return new ArrayList<>(observers);
     }
 
     /**

src/main/java/org/apache/commons/io/monitor/FileAlterationObserver.java

@@ -19,6 +19,7 @@
 import java.io.File;
 import java.io.FileFilter;
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.List;
@@ -394,7 +395,7 @@ public FileFilter getFileFilter() {
      * @return The file system listeners
      */
     public Iterable<FileAlterationListener> getListeners() {
-        return listeners;
+        return new ArrayList<>(listeners);
     }
 
     /**