1.使用for循环遍历

    public static void main(String[] args) {int limit = 5;List<Integer> oldList = Lists.newArrayList(1, 2, 3, 4, 5, 6, 7);List<Integer> newList = Lists.newArrayList();if (oldList.size() <= limit) {newList.addAll(oldList);return;}for (int i = 0; i < limit; i++) {newList.add(oldList.get(i))}}

2.使用Stream API

    public static void main(String[] args) {int limit = 5;List<Integer> oldList = Lists.newArrayList(1, 2, 3, 4, 5, 6, 7);List<Integer> newList = new ArrayList<>(limit);if (oldList.size() <= limit) {newList.addAll(oldList);return;}newList = oldList.stream().limit(limit).collect(Collectors.toList());}

    
3.使用subList方法    

    public static void main(String[] args) {int limit = 5;List<Integer> oldList = Lists.newArrayList(1, 2, 3, 4, 5, 6, 7);List<Integer> newList = new ArrayList<>(limit);if (oldList.size() <= limit) {newList.addAll(oldList);return;}newList = oldList.subList(0,limit);}

    
4.使用Apache Commons Collections

    public static void main(String[] args) {int limit = 5;List<Integer> oldList = Lists.newArrayList(1, 2, 3, 4, 5, 6, 7);List<Integer> newList = new ArrayList<>(limit);if (oldList.size() <= limit) {newList.addAll(oldList);return;}CollectionUtils.addAll(newList, oldList.iterator());}