删除ArrayList中重复元素

用Set ,倘若list里边的元素不是基本数据类型而是对象,那么请覆写Object的boolean equals(Object obj) 和int hashCode()方法.

returnnewArrayList(newHashSet(list)); 

方法一：循环元素删除

//删除ArrayList中重复元素
publicstaticvoidremoveDuplicate(List list){
  for(inti=0; i<list.size()-1; i++){
   for(intj=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
publicstaticvoidremoveDuplicate(List list){
     HashSet h=newHashSet(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
publicstaticvoidremoveDuplicateWithOrder(List list){
    Set set=newHashSet();
     List newList=newArrayList();
  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);
}