Fix SpotBugs errors

- [ERROR] Medium:
org.apache.commons.io.file.AccumulatorPathVisitor.getDirList() may
expose internal representation by returning
AccumulatorPathVisitor.dirList [org.apache.commons.io.file.AccumulatorPathVisitor]
At AccumulatorPathVisitor.java:[line 179] EI_EXPOSE_REP
- [ERROR] Medium:
org.apache.commons.io.file.AccumulatorPathVisitor.getFileList() may
expose internal representation by returning
AccumulatorPathVisitor.fileList [org.apache.commons.io.file.AccumulatorPathVisitor]
At AccumulatorPathVisitor.java:[line 188] EI_EXPOSE_REP

Author: garydgregory

src/changes/changes.xml

@@ -64,6 +64,8 @@ The <action> type attribute can be add,update,fix,remove.
       <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>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.IOExceptionList.getCauseList() may expose internal representation by returning IOExceptionList.causeList [org.apache.commons.io.IOExceptionList] At IOExceptionList.java:[line 118] EI_EXPOSE_REP.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.IOExceptionList.getCauseList(Class) may expose internal representation by returning IOExceptionList.causeList [org.apache.commons.io.IOExceptionList] At IOExceptionList.java:[line 129] EI_EXPOSE_REP.</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.file.AccumulatorPathVisitor.getDirList() may expose internal representation by returning AccumulatorPathVisitor.dirList [org.apache.commons.io.file.AccumulatorPathVisitor] At AccumulatorPathVisitor.java:[line 179] EI_EXPOSE_REP.</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix SpotBugs error: org.apache.commons.io.file.AccumulatorPathVisitor.getFileList() may expose internal representation by returning AccumulatorPathVisitor.fileList [org.apache.commons.io.file.AccumulatorPathVisitor] At AccumulatorPathVisitor.java:[line 188] EI_EXPOSE_REP.</action>
       <!-- UPDATE -->
       <action dev="ggregory" type="update" due-to="Gary Gregory">Bump org.codehaus.mojo:exec-maven-plugin from 3.1.0 to 3.1.1 #512.</action>
       <action dev="ggregory" type="update" due-to="Gary Gregory">Bump commons-lang3 from 3.13.0 to 3.14.0.</action>      

src/main/java/org/apache/commons/io/file/AccumulatorPathVisitor.java

@@ -171,21 +171,21 @@ public boolean equals(final Object obj) {
     }
 
     /**
-     * Gets the list of visited directories.
+     * Gets a copy of the list of visited directories.
      *
-     * @return the list of visited directories.
+     * @return a copy of the list of visited directories.
      */
     public List<Path> getDirList() {
-        return dirList;
+        return new ArrayList<>(dirList);
     }
 
     /**
-     * Gets the list of visited files.
+     * Gets a copy of the list of visited files.
      *
-     * @return the list of visited files.
+     * @return a copy of the list of visited files.
      */
     public List<Path> getFileList() {
-        return fileList;
+        return new ArrayList<>(fileList);
     }
 
     @Override