HashMap按照键值key排序

Map map = new HashMap();
map.put("4", "a");
map.put("2", "b");
map.put("1", "c");
map.put("3", "d");

第一种方法：

Object[] key =  map.keySet().toArray();  
Arrays.sort(key);  

for(int i = 0; i<key.length; i++)
{  
     System.out.println(map.get(key[i]));  
}

第二种方法：

List arrayList = new ArrayList(map.entrySet());

Collections.sort(arrayList, new Comparator() 
{
  public int compare(Object arg1, Object arg2) 
 {
    Map.Entry obj1 = (Map.Entry) arg1;
    Map.Entry obj2 = (Map.Entry) arg2;
    return (obj1.getKey()).toString().compareTo(obj2.getKey());
  }
});
//将HASHMAP中的数据排序
for (Iterator iter = arrayList.iterator(); iter.hasNext();) 
{
   Map.Entry entry = (Map.Entry)iter.next();
   String  key = (String)entry.getKey();
   System.out.println(map.get(key));  
}