### Question:
HttpHeaderHelper { public static String mapCharset(String enc) { return mapCharset(enc, ISO88591); } private  HttpHeaderHelper(); static List<String> getHeader(Map<String, List<String>> headerMap, String key); static String getHeaderKey(final String key); static String findCharset(String contentType); static String mapCharset(String enc); static String mapCharset(String enc, String deflt); static final String ACCEPT_ENCODING; static final String CONTENT_TYPE; static final String CONTENT_ID; static final String CONTENT_ENCODING; static final String CONTENT_LENGTH; static final String CONTENT_TRANSFER_ENCODING; static final String COOKIE; static final String TRANSFER_ENCODING; static final String CHUNKED; static final String CONNECTION; static final String CLOSE; static final String AUTHORIZATION; }### Answer:
@Test public void testMapCharset() { final String charset = StandardCharsets.UTF_8.name(); String cs = HttpHeaderHelper.mapCharset(charset); assertEquals(charset, cs); cs = HttpHeaderHelper.mapCharset("\"" + charset + "\""); assertEquals(charset, cs); cs = HttpHeaderHelper.mapCharset("'" + charset + "'"); assertEquals(charset, cs); cs = HttpHeaderHelper.mapCharset(null); assertEquals(HttpHeaderHelper.ISO88591, cs); cs = HttpHeaderHelper.mapCharset("''"); assertEquals(HttpHeaderHelper.ISO88591, cs); cs = HttpHeaderHelper.mapCharset("wrong-charset-name"); assertNull(cs); }