Set转List,List转Set,数组转List,List转数组

Set转List:

HashSet<Long> set = new HashSet<>();
ArrayList<Long> longs = new ArrayList<>(set);

List转Set:

List<String> strings1 = new ArrayList<>();
Set<Object> objects = new HashSet<>(strings1);

 

数组转List:  (小提示：数组因为已经固定大小，所以转成List后不能做增删add、remove等操作，会报异常的)

 String[] strings = {"a", "b", "c"};
 List<String> strings1 = Arrays.asList(strings);

 

List转数组：

 List<String> strings1 = new ArrayList<>();
 Object[] objects = strings1.toArray();

 

数组转Set :

 String[] strings = {"a", "b", "c"};
 HashSet<String> stringHashSet = new HashSet<>(Arrays.asList(strings));