### Question:
WebUtil { public static String guessContentType(String fileName) { return URLConnection.getFileNameMap().getContentTypeFor(fileName); }  static String guessContentType(String fileName); static String encodeContentDisposition(String userAgent, String fileName);  }### Answer:
@Test public void testGuessContentType() throws Exception { assertEquals(WebUtil.guessContentType("1.jpg"), "image/jpeg"); assertNull(WebUtil.guessContentType("2.xlsx")); assertEquals(WebUtil.guessContentType("3.png"), "image/png"); assertNull(WebUtil.guessContentType("4.csv")); assertEquals(WebUtil.guessContentType("5.zip"), "application/zip"); assertEquals(WebUtil.guessContentType("6.txt"), "text/plain"); assertNull(WebUtil.guessContentType("7.docx")); assertNull(WebUtil.guessContentType("8.doc")); assertNull(WebUtil.guessContentType("9.ppt")); assertEquals(WebUtil.guessContentType("10.pdf"), "application/pdf"); assertNull(WebUtil.guessContentType("11.xls")); }