List、Set、Map、数组之间各种转换

List转Set       

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

Set转List   

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

数组转为List     

1.List arr = Arrays.asList("1", "2", "3");


2.//或者

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

4.List list = Arrays.asList(arr);

数组转为Set        

1.int[] arr = { 1, 2, 3 };

2.Set set = new HashSet(Arrays.asList(arr));

Map的值转化为List        

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

Map的值转化为Set         

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

List转数组          

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

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