### Question:
FileUtils { public static String cleanFileName(String fileName) { if (fileName == null) return fileName; return fileName.replaceAll("[\\\\/:*?\"<>|]", ""); }  static void copyDir(final String src, final String dest); static void copyDir(final File src, final File dest); static void copyFile(final String src, final String dest); static boolean renameFile(String oldPath, String newPath); static void copyFile(final File src, final File dest); static String cleanFileName(String fileName); static File copyToTempFile(String filename, Class resourceLocation, File tempDir);  }### Answer:
@Test public void testCleanFileName() throws IOException { assertEquals("abcdefghijk", FileUtils.cleanFileName("a\\b/c:d*e?f\"g<h>i|jk")); String fileName = null; assertNull(FileUtils.cleanFileName(fileName)); }