Java中List集合去除重复数据的四种方法

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;

    }