1.java8获取list集合中重复的元素 //单独String集合 List list = Arrays.asList("a","b","a","c","d","b"); List collect
//单独String集合 List<String> list = Arrays.asList("a","b","a","c","d","b"); List<String> collect = list.stream().filter(i -> i != "") // list 对应的 Stream 并过滤"" .collect(Collectors.toMap(e -> e, e -> 1, Integer::sum)) // 获得元素出现频率的 Map,键为元素,值为元素出现的次数 .entrySet() .stream() // 所有 entry 对应的 Stream .filter(e -> e.getValue() > 1) // 过滤出元素出现次数大于 1 (重复元素)的 entry .map(Map.Entry::geTKEy) // 获得 entry 的键(重复元素)对应的 Stream .collect(Collectors.toList()); System.out.println(collect);
List<Person> personList = new ArrayList<Person>(); personList.add(new Person("张三", 8, 3000)); personList.add(new Person("李四", 18, 5000)); personList.add(new Person("王五", 28, 7000)); personList.add(new Person("孙六", 38, 9000)); personList.add(new Person("孙六", 38, 9000)); personList.add(new Person("孙六", 38, 10000)); //1.先根据得到一个属于集合 姓名 List<String> uniqueList = personList.stream().collect(Collectors.groupingBy(Person::getName, Collectors.counting())) .entrySet().stream().filter(e -> e.getValue() > 1) .map(Map.Entry::getKey).collect(Collectors.toList()); uniqueList.forEach(p -> System.out.println(p)); //计算两个list中的重复值 3条数据 List<Person> reduce1 = personList.stream().filter(item -> uniqueList.contains(item.getName())).collect(Collectors.toList()); System.out.println(reduce1.toString()); //2.根据多个属性获取重复数据,只能重复操作得到重复的数据 工资 List<Integer> collect1 = reduce1.stream().collect(Collectors.groupingBy(Person::getWages, Collectors.counting())) .entrySet().stream().filter(e -> e.getValue() > 1) .map(Map.Entry::getKey).collect(Collectors.toList()); //计算两个list中的差集 List<Person> collect2 = reduce1.stream().filter(item -> collect1.contains(item.getWages())).collect(Collectors.toList()); System.out.println(collect2.toString());
结果: 根据多个属性获取重复数据,还在摸索中,欢迎大家来指点!!!!!
List<Person> personList = new ArrayList<Person>(); personList.add(new Person("张三", 8, 3000)); personList.add(new Person("李四", 18, 5000)); personList.add(new Person("王五", 28, 7000)); personList.add(new Person("孙六", 38, 9000)); personList.add(new Person("孙六", 38, 9000)); personList.add(new Person("孙六", 38, 10000)); //去重 List<Person> unique = personList.stream().collect(Collectors.collectingAndThen( Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Person::getName))), ArrayList::new)); System.out.println("unique:"+unique.toString());
结果:
来源地址:https://blog.csdn.net/qq_41128049/article/details/127129690
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本文标题: JAVA8 获取list集合中重复的元素和获取去重数据
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