List<Integer> list1 = Arrays.asList(1, 2, 3, 4); List<Integer> list2 = Arrays.asList(3, 4, 5, 6); List<Integer> intersection = CollectionUtils.intersection(list1, list2); String str = " "; boolean isEmpty = StringUtils.isBlank(str); Date today = new Date(); Date previousDay = DateUtils.addDays(today, -1);