去除List中重复的元素

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.

return new ArrayList(new HashSet(list)); 

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);
}