### Question:
CSVFormatter { public static String formatLine(List<String> values, char separator) { boolean first = true; StringBuilder builder = new StringBuilder(); for (String value : values) { if (!first) { builder.append(separator); } builder.append(followCsvStandard(value)); first = false; } return builder.append(System.lineSeparator()).toString(); } private  CSVFormatter(); static String formatLine(List<String> values, char separator); static String formatLine(List<String> values, char separator, char customQuote); static final char SEPARATOR; }### Answer:
@Test public void formatLine() { List<String> values = Arrays.asList("aaa", "bbb", "ccc", "aa", "bb", "cc", "a", "b", "c"); String expected = "aaa,bbb,ccc,aa,bb,cc,a,b,c\n"; String actual = CSVFormatter.formatLine(values, ','); assertEquals(expected, actual); }
@Test public void formatLineWithCustomQuote() { List<String> values = Arrays.asList("aaa", "bbb", "ccc", "aa", "bb", "cc", "a", "b", "c"); String expected = "\"aaa\",\"bbb\",\"ccc\",\"aa\",\"bb\",\"cc\",\"a\",\"b\",\"c\"\n"; String actual = CSVFormatter.formatLine(values, ',', '"'); assertEquals(expected, actual); }