Avoid NullPointerException in RegexFileFilter.RegexFileFilter(Pattern).

Avoid NullPointerException in RegexFileFilter.accept(Path,
BasicFileAttributes)

Author: garydgregory

src/changes/changes.xml

@@ -53,6 +53,8 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="fix" due-to="Stephan Markwalder, Gary Gregory">Add test for FileChannels.contentEquals() #509.</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix FileChannels.contentEquals().</action>
       <action dev="ggregory" type="fix" due-to="Gary Gregory">Fix some Javadoc issues in LineIterator and IOUtils.</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Avoid NullPointerException in RegexFileFilter.RegexFileFilter(Pattern).</action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">Avoid NullPointerException in RegexFileFilter.accept(Path, BasicFileAttributes).</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 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>
       <!-- UPDATE -->

src/main/java/org/apache/commons/io/filefilter/RegexFileFilter.java

@@ -111,7 +111,7 @@ private static int toFlags(final IOCase ioCase) {
      */
     @SuppressWarnings("unchecked")
     public RegexFileFilter(final Pattern pattern) {
-        this(pattern, (Function<Path, String> & Serializable) p -> p.getFileName().toString());
+        this(pattern, (Function<Path, String> & Serializable) p -> Objects.toString(p.getFileName(), null));
     }
 
     /**
@@ -125,7 +125,7 @@ public RegexFileFilter(final Pattern pattern) {
     public RegexFileFilter(final Pattern pattern, final Function<Path, String> pathToString) {
         Objects.requireNonNull(pattern, "pattern");
         this.pattern = pattern;
-        this.pathToString = pathToString;
+        this.pathToString = pathToString != null ? pathToString : Objects::toString;
     }
 
     /**
@@ -181,7 +181,8 @@ public boolean accept(final File dir, final String name) {
      */
     @Override
     public FileVisitResult accept(final Path path, final BasicFileAttributes attributes) {
-        return toFileVisitResult(pattern.matcher(pathToString.apply(path)).matches());
+        final String result = pathToString.apply(path);
+        return toFileVisitResult(result != null && pattern.matcher(result).matches());
     }
 
     /**

src/test/java/org/apache/commons/io/filefilter/RegexFileFilterTest.java

@@ -166,7 +166,9 @@ public void testRegexFileNameOnly() throws IOException {
         final String patternStr = "Foo.*";
         assertFiltering(assertSerializable(new RegexFileFilter(patternStr)), path, true);
         assertFiltering(assertSerializable(new RegexFileFilter(Pattern.compile(patternStr), (Function<Path, String> & Serializable) Path::toString)), path,
-            false);
+                false);
+        assertFiltering(new RegexFileFilter(Pattern.compile(patternStr), (Function<Path, String> & Serializable) null), path, false);
+        assertFiltering(new RegexFileFilter(Pattern.compile(patternStr), (Function<Path, String> & Serializable) p -> null), path, false);
     }
 
 }