### Question:
Sets { public static final Set<String> fromCommaSeparatedValues(String csv) { if (csv == null || csv.isEmpty()) { return Collections.EMPTY_SET; } String[] tokens = csv.split(","); return new HashSet<String>(Arrays.asList(tokens)); }  static final Set fromMap(Map map, Object... keys); static final Set<String> fromCommaSeparatedValues(String csv);  }### Answer:
@Test public void testFromCommaSeparatedValues() { Set s = Sets.fromCommaSeparatedValues("1,2,3"); assertTrue(s.contains("1")); assertTrue(s.contains("2")); assertTrue(s.contains("3")); assertEquals(3, s.size()); }
@Test public void testFromCommaSeparatedValues_NullInput() { assertEquals(Collections.EMPTY_SET, Sets.fromCommaSeparatedValues(null)); }
@Test public void testFromCommaSeparatedValues_EmptyInput() { assertEquals(Collections.EMPTY_SET, Sets.fromCommaSeparatedValues("")); }