@Test void testComparator(){ Comparator<String> comparator = new Comparator<String>() { @Override public int compare(String str1, String str2) { if (str1 == null && str2 == null) { return 0; } if (str1 == null) { return 1; } if (str2 == null) { return -1; } return str2.compareTo(str1); } }; SortedArrayList<String> list = new SortedArrayList<>(comparator); assertNotNull(list.getComparator()); list.add("aaa"); list.add("bbb"); assertEquals(2, list.size()); assertEquals("bbb", list.get(0)); assertEquals("aaa", list.get(1)); } }