list,set,map,数组间的相互转换

 

java各种集合之间的互相转换：

1.list转set

 

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

2.set转list

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

 

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

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));