Java 两个List集合取交集 并集

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/**      * @Description: 取交集      * @Param: [list1, list2]      * @Return: java.util.List<java.lang.String>      * @Author:      * @Date: 2022/6/28 15:35      **/     public List<String> getAndRes(List<String> list1, List<String> list2) {         if (null != list1 && list1.size() != 0) {             if (null == list2 || list2.size() == 0) {                 return list1;             } else {                 return list1.stream().filter(list2::contains).collect(Collectors.toList());             }         } else {             return list2;         }     } <br>     /**      * @Description: 取并集      * @Param: [list1, list2]      * @Return: java.util.List<java.lang.String>      * @Author:      * @Date: 2022/6/28 15:35      **/     public List<String> getORRes(List<String> list1, List<String> list2) {         list1.addAll(list2);         return list1.stream().distinct().collect(Collectors.toList());     }