循环有关问题

循环问题;
如下:
ArrayList   al=new   ArrayList();
al.Add( "lei ");
al.Add( "wanglei ");
al.Add( "wanghao ");
al.Add( "wanglei ");
al.Add( "wanghao ");

如果我想除去里面的重复的   应该怎么做啊   ,注意   ,里面al里面的值的条数是不确定的啊!~

[解决办法]
1.The removeDuplicate Method:
/** List order not maintained **/
public static void removeDuplicate(ArrayList arlList)
{
HashSet h = new HashSet(arlList);
arlList.clear();
arlList.addAll(h);
}


2.The removeDuplicateWithOrder Method:
/** List order maintained **/
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()
[解决办法]
ArrayList al2=new ArrayList();
for(int i=0;i <al.Count;i++)
{
if(!al2.Contrains(al[i])
al2.Add(al[i]);
}

al = al2;
[解决办法]
ArrayList al=new ArrayList();al.Add( "lei ");al.Add( "wanglei ");al.Add( "wanghao ");al.Add( "wanglei ");al.Add( "wanghao ");al.Sort();for(int i=1;i <al.Count;i++){if(al[i].ToString() == al[i-1].ToString()){al.RemoveAt(i);i--;}}for(int i=0;i <al.Count;i++){Response.Write(al[i].ToString()+ " <BR> ");}