### Question:
FileUtils { public static String sanitizeFilename(String filename) { if (filename == null || filename.isEmpty()) { return filename; } int codePointCount = filename.codePointCount(0, filename.length()); final StringBuilder cleanName = new StringBuilder(); for (int i = 0; i < codePointCount; i++) { int c = filename.codePointAt(i); if (Arrays.binarySearch(INVALID_CHARS, c) < 0) { cleanName.appendCodePoint(c); } else { cleanName.append('_'); } } return cleanName.toString(); }  static void closeQuietly(final Closeable closeable); static void releaseQuietly(final FileLock lock); @Deprecated static void ensureDirectoryExistAndCanAccess(final File dir); static void ensureDirectoryExistAndCanReadAndWrite(final File dir); static void ensureDirectoryExistAndCanRead(final File dir); static long copyFile(final File source, final File destination, final boolean lockInputFile, final boolean lockOutputFile, final boolean move, final Logger logger); static long copyFile(final File source, final File destination, final boolean lockInputFile, final boolean lockOutputFile, final Logger logger); static long copyFile(final File source, final OutputStream stream, final boolean closeOutputStream, final boolean lockInputFile); static long copyFile(final InputStream stream, final File destination, final boolean closeInputStream, final boolean lockOutputFile); static boolean deleteFile(final File file, final Logger logger); static boolean deleteFile(final File file, final Logger logger, final int attempts); static void deleteFilesInDirectory(final File directory, final FilenameFilter filter, final Logger logger); static void deleteFilesInDirectory(final File directory, final FilenameFilter filter, final Logger logger, final boolean recurse); static void deleteFilesInDirectory(final File directory, final FilenameFilter filter, final Logger logger, final boolean recurse, final boolean deleteEmptyDirectories); static void deleteFiles(final Collection<File> files, final boolean recurse); static void deleteFile(final File file, final boolean recurse); static void sleepQuietly(final long millis); static String sanitizeFilename(String filename); static final long TRANSFER_CHUNK_SIZE_BYTES; static final long MILLIS_BETWEEN_ATTEMPTS; }### Answer:
@Test public void testSanitizeFilename() { String filename = "This / is / a test"; final String sanitizedFilename = FileUtils.sanitizeFilename(filename); assertEquals("This___is___a_test", sanitizedFilename); }