//list转数组
        List<String> list = new ArrayList<>();
        list.add("1");
        list.add("2");
        list.add("3");
        String[] strings = new String[list.size()];
        list.toArray(strings);
        for (int i = 0; i < strings.length; i++) {
            System.out.println(strings[i]);
        }
//数组转list
        String[] strings1 = {"7","8","9"};
        List<String> list1 = Arrays.asList(strings1);
        list1.forEach(l->{
            System.out.println(l);
        });