对List《实体类》重复值的操作

墨蓝 2023-09-28 16:08 14阅读 0赞

## 对List<实体类>重复值的操作 ##

### 判断是否有重复：（Boolean） ###

public Boolean JudgeStopWatchValue(List<StopWatchValue> stopWatchValues) {
        
            AtomicReference<Boolean> flag = new AtomicReference<>(true);
            //判断码值编码是否重复
            // 根据指定属性分组，并统计数量（key：指定属性，value：数量）
            Map<Object, Long> mapGroup = stopWatchValues.stream().collect(Collectors.groupingBy(StopWatchValue::getcValue, Collectors.counting()));
            // 筛选Map中value大于1的key
            Stream<Object> stringStream = mapGroup.entrySet().stream().filter(entry -> entry.getValue() > 1).map(Map.Entry::getKey);
            stringStream.forEach(str -> {
        
                if (str!=null){
        
                    flag.set(false);
                }
            });
            return flag.get();
        }

### 查重： ###

public static void main(String[] args) {
        
    		 Person person1 = new Person("小刘", 24, "男");
            Person person2 = new Person("小贺", 18, "女");
            Person person3 = new Person("小袁", 18, "女");
            Person person4 = new Person("小李", 21, "男");
            Person person5 = new Person("小子", 21, "男");
            List<Person> persons = Arrays.asList(person1, person2, person3, person4,person5);
    
            // 根据指定属性分组，并统计数量（key：指定属性，value：数量）
            Map<Object, Long> mapGroup = persons.stream().collect(Collectors.groupingBy(person -> person.getAge(), Collectors.counting()));
            System.out.println(mapGroup.toString());
    
            // 筛选Map中value大于1的key
            Stream<Object> stringStream = mapGroup.entrySet().stream().filter(entry -> entry.getValue() > 1).map(entry -> entry.getKey());
            System.out.print("重复的数据：{ ");
            stringStream.forEach(str -> {
        
                System.out.print(str + " ");
            });
            System.out.println("}");
    	}

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FzbXljYXQ_size_16_color_FFFFFF_t_70]

## 去重： ##

public static void main(String[] args) {
        
            Map map1=new HashMap();
            Map map2=new HashMap();
            Map map3=new HashMap();
            map1.put("name","Jam");
            map1.put("age","20");
            map2.put("name","Jam");
            map2.put("age","20");
            map3.put("name","Jam");
            map3.put("age","20");
            List testList=new ArrayList();
            testList.add(map1);
            testList.add(map2);
            testList.add(map2);
            System.out.println("去重前");
            System.out.println(testList);
            //java8去重
            testList= (List) testList.stream().distinct().collect(Collectors.toList());
            System.out.println("去重后");
            System.out.println(testList);
        }

参考文章：[List集合中对象属性判重\_快了的码农的博客-CSDN博客\_list判重][List_-CSDN_list]

参考文章：[如何优雅的判断List集合中对象的某个字段是否存在重复值\_wanna do的博客-CSDN博客\_判断list对象某个属性值是否重复][List_wanna do_-CSDN_list]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FzbXljYXQ_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/202105051321452.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FzbXljYXQ=,size_16,color_FFFFFF,t_70
[List_-CSDN_list]: https://blog.csdn.net/weixin_43966996/article/details/124603366
[List_wanna do_-CSDN_list]: https://blog.csdn.net/asmycat/article/details/102571984?spm=1001.2101.3001.6650.1&utm_medium=distribute.pc_relevant.none-task-blog-2~default~CTRLIST~default-1-102571984-blog-107769078.pc_relevant_multi_platform_whitelistv1&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2~default~CTRLIST~default-1-102571984-blog-107769078.pc_relevant_multi_platform_whitelistv1&utm_relevant_index=2