public static void removeDuplicate(List list) { 
for ( int i = 0 ; i < list.size() - 1 ; i ++ ) { 
for ( int j = list.size() - 1 ; j > i; j -- ) { 
if (list.get(j).equals(list.get(i))) { 
list.remove(j); 
} 
} 
} 
System.out.println(list); 
}

public static void removeDuplicate(List list) { 
HashSet h = new HashSet(list); 
list.clear(); 
list.addAll(h); 
System.out.println(list); 
} 

public static void removeDuplicateWithOrder(List list) { 
Set set = new HashSet(); 
List newList = new ArrayList(); 
for (Iterator iter = list.iterator(); iter.hasNext();) { 
Object element = iter.next(); 
if (set.add(element)) 
newList.add(element); 
} 
list.clear(); 
list.addAll(newList); 
System.out.println( " remove duplicate " + list); 
} 

publi List<String> getNewList(List<String> li){
List<String> list = new ArrayList<String>();
for(int i=0; i<li.size(); i++){
String str = li.get(i); //獲取傳入集合對象的每一個元素
if(!list.contains(str)){ //查看新集合中是否有指定的元素，如果沒有則加入
list.add(str);
}
}
return list; //返回集合
}
public class Test{
public static void main(String[] args){
ArrayList<String> arr = new ArrayList<String>();
arr.add("aaa");
arr.add("bbb");
arr.add("aaa");
arr.add("ccc");
arr = getNewList(arr); //方法去重
System.out.println(arr);
}
}