list,set,map,数组间的相互转换

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");  

此时stooges中有有三个元素。
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");   
System.out.println(list);   
           
String[] arr = (String[])list.toArray(new String[list.size()]);   
System.out.println(Arrays.toString(arr));