1.list转set

Set set = new HashSet(new ArrayList());

2.set转list

List list = new ArrayList(new HashSet());

3.数组转为list

List stooges = Arrays.asList("Larry", "Moe", "Curly");

或者

String[] arr = {"1", "2"};

List list = Arrays.asList(arr);

4.数组转为set

int[] a = { 1, 2, 3 };

Set set = new HashSet(Arrays.asList(a));

5.map的相关操作。

Map map = new HashMap();

map.put("1", "a");

map.put('2', 'b');

map.put('3', 'c');

System.out.println(map);

// 输出所有的值

System.out.println(map.keySet());

// 输出所有的键

System.out.println(map.values());

// 将map的值转化为List

List list = new ArrayList(map.values());

System.out.println(list);

// 将map的值转化为Set

Set set = new HashSet(map.values());

System.out.println(set);

6.list转数组

List list = Arrays.asList("a","b");

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

System.out.println(Arrays.toString(arr));