java list,set,map,数组间的相互转换详解

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

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

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

String[] arr = { "1" , "2" }; 
List list = Arrays.asList(arr); 

int [] a = { 1 , 2 , 3 }; 
Set set = new HashSet(Arrays.asList(a)); 

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); 

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));