List集合去重复

//  返回的List是无序
HashSet<String> set = new  HashSet<String>(list);        
list.clear();        
list.addAll(set);        
return list;  

//  返回的List是有序
LinkedHashSet<String> set = new  LinkedHashSet<String>(list);        
list.clear();        
list.addAll(set);        
return list;