List、Set、Map、数组互转

在这之前先说下List去重复：

	public static void removeDuplicate(ArrayList arlList) {
		HashSet h = new HashSet(arlList);
		arlList.clear();
		arlList.addAll(h);
	}

	public static void removeDuplicateWithOrder(ArrayList arlList) {
		Set set = new HashSet();
		List newList = new ArrayList();
		for (Iterator iter = arlList.iterator(); iter.hasNext();) {
			Object element = iter.next();
			if (set.add(element))
				newList.add(element);
		}
		arlList.clear();
		arlList.addAll(newList);
	}

看了List去重复后再理解之间的互转就明白了，下面之间的互转：

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");  

4.数组转为set 

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

5.list转数组

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

6.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);

                               图一

                      

                                 图二