List<String> arrayList = new ArrayList<>(); LinkedList<String> linkedList = new LinkedList<>(); List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5); List<Integer> evenSquares = numbers.stream() .filter(n -> n % 2 == 0) .map(n -> n * n) .collect(Collectors.toList()); int sum = 0; List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5); for (int i : numbers) { sum += i; } ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>(); map.put("key1", 1); map.put("key2", 2); map.putIfAbsent("key1", 3); Connection connection = dataSource.getConnection();