JAVA8 List＜List＜Integer＞＞ list中再装一个list转成一个list

		List<Integer> collect = IntStream.range(1, 10).boxed().collect(Collectors.toList());
        List<Integer> collect1 = IntStream.range(10, 20).boxed().collect(Collectors.toList());

        List<List<Integer>> lists = new ArrayList<>();
        lists.add(collect);
        lists.add(collect1);
        ArrayList<Integer> collect2 = lists.stream().collect(ArrayList::new, ArrayList::addAll, ArrayList::addAll);
        System.out.println(collect2);