补充一下： Long[] arrayLong = (Long[]) ids.toArray();

如果报错。那就用

Long[] arrayLong =  ids.toArray(new Long[0]);

List转数组

List<Long> ids = new ArrayList<Long>();
Object[] array = ids.toArray();
//泛型需要强转
Long[] arrayLong = (Long[]) ids.toArray();

数组转list

List<Long> list = Arrays.asList(arrayLong);

即可，