(转)java8实现对象列表去重
java8实现列表去重,java8的stream和lambda的使用实例
通过普通的方式也可以达到去重的效果,但是借助java8新特性可以很方便的实现列表去重,测试demo如下
实体类:
public class Person { private int id; private String name; private int age; public Person() { } public Person(int id, String name, int age) { this.id = id; this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public int getId() { return id; } public void setId(int id) { this.id = id; }
@Override public String toString() { return "Person{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + '}'; } }
测试:
List<Person> persons = new ArrayList(); List<Integer> ids = new ArrayList<>();//用来临时存储person的id persons.add(new Person(1, "name1", 10)); persons.add(new Person(2, "name2", 21)); persons.add(new Person(5, "name5", 55)); persons.add(new Person(3, "name3", 34)); persons.add(new Person(1, "name1", 10)); List<Person> personList = persons.stream().filter(// 过滤去重 v -> { boolean flag = !ids.contains(v.getId()); ids.add(v.getId()); return flag; } ).collect(Collectors.toList()); System.out.println(personList);
还可以实现条件过滤和列表排序:
//获取person集合中的所有大于18周岁,并排序 List<Person> personList= new ArrayList(); personList.add(new Person(1, "name1", 10)); personList.add(new Person(2, "name2", 21)); personList.add(new Person(5, "name5", 55)); personList.add(new Person(3, "name3", 34)); personList.add(new Person(4, "name4", 6)); personList.stream() .filter(p -> p.getAge() >= 18)//获取所有18岁以上的用户 //.sorted(Comparator.comparing(Person::getAge))//依年纪升序排序 .sorted(Comparator.comparing(Person::getAge).reversed())//依年纪降序排序 .collect(Collectors.toList()); System.out.println(personList);
转自:https://www.jianshu.com/p/63d2db850a8d