Java实现ArrayList去重复值

方法一：循环元素删除 

//  删除ArrayList中重复元素
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);
}

方法二：通过HashSet剔除

//  删除ArrayList中重复元素
  public   static   void  removeDuplicate(List list)   {
    HashSet h  =   new  HashSet(list);
    list.clear();
    list.addAll(h);
    System.out.println(list);
}

方法三： 删除ArrayList中重复元素，保持顺序

// 删除ArrayList中重复元素，保持顺序
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);
}