//list转long数组
List<Long> list = new ArrayList<>();

 Long[] skuIds = list.toArray(new Long[list.size()]);

//list转string数组

List<String> list = new ArrayList<String>();

        list.add("a1");

        list.add("a2");

        String[] toBeStored = list.toArray(new String[list.size()]);

        for (String str : toBeStored) {

            System.out.println(str);

        }