### Question:
DataUtil { static String getCharsetFromContentType(String contentType) { if (contentType == null) return null; Matcher m = charsetPattern.matcher(contentType); if (m.find()) { String charset = m.group(1).trim(); charset = charset.replace("charset=", ""); return validateCharset(charset); } return null; } private  DataUtil(); static Document load(File in, String charsetName, String baseUri); static Document load(InputStream in, String charsetName, String baseUri); static Document load(InputStream in, String charsetName, String baseUri, Parser parser); static ByteBuffer readToByteBuffer(InputStream inStream, int maxSize);  }### Answer:
@Test public void testCharset() { assertEquals("utf-8", DataUtil.getCharsetFromContentType("text/html;charset=utf-8 ")); assertEquals("UTF-8", DataUtil.getCharsetFromContentType("text/html; charset=UTF-8")); assertEquals("ISO-8859-1", DataUtil.getCharsetFromContentType("text/html; charset=ISO-8859-1")); assertEquals(null, DataUtil.getCharsetFromContentType("text/html")); assertEquals(null, DataUtil.getCharsetFromContentType(null)); assertEquals(null, DataUtil.getCharsetFromContentType("text/html;charset=Unknown")); }
@Test public void testQuotedCharset() { assertEquals("utf-8", DataUtil.getCharsetFromContentType("text/html; charset=\"utf-8\"")); assertEquals("UTF-8", DataUtil.getCharsetFromContentType("text/html;charset=\"UTF-8\"")); assertEquals("ISO-8859-1", DataUtil.getCharsetFromContentType("text/html; charset=\"ISO-8859-1\"")); assertEquals(null, DataUtil.getCharsetFromContentType("text/html; charset=\"Unsupported\"")); assertEquals("UTF-8", DataUtil.getCharsetFromContentType("text/html; charset='UTF-8'")); }
@Test public void shouldNotThrowExceptionOnEmptyCharset() { assertEquals(null, DataUtil.getCharsetFromContentType("text/html; charset=")); assertEquals(null, DataUtil.getCharsetFromContentType("text/html; charset=;")); }
@Test public void shouldSelectFirstCharsetOnWeirdMultileCharsetsInMetaTags() { assertEquals("ISO-8859-1", DataUtil.getCharsetFromContentType("text/html; charset=ISO-8859-1, charset=1251")); }
@Test public void shouldCorrectCharsetForDuplicateCharsetString() { assertEquals("iso-8859-1", DataUtil.getCharsetFromContentType("text/html; charset=charset=iso-8859-1")); }
@Test public void shouldReturnNullForIllegalCharsetNames() { assertEquals(null, DataUtil.getCharsetFromContentType("text/html; charset=$HJKDF§$/(")); }