Java中List集合去除重复数据的四种方法

1. 循环list中的所有元素然后删除重复

 

public   static   List  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);
            }
        }
      }
    return list;
}  

 

2. 通过HashSet踢除重复元素

 

public static List removeDuplicate(List list) {
    HashSet h = new HashSet(list);
    list.clear();
    list.addAll(h);
    return list;
}   

 

3. 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);
 }   

 

4.把list里的对象遍历一遍，用list.contains()，如果不存在就放入到另外一个list集合中

 

public static List removeDuplicate(List list){
        List listTemp = new ArrayList();
        for(int i=0;i<list.size();i++){
            if(!listTemp.contains(list.get(i))){
                listTemp.add(list.get(i));
            }
        }
        return listTemp;
    }