（轉）java8實現對象列表去重

java8實現列表去重，java8的stream和lambda的使用實例

通過普通的方式也可以達到去重的效果，但是借助java8新特性可以很方便的實現列表去重，測試demo如下

實體類：

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 +
                '}';
    }
}

測試：

       List<Person> persons = new ArrayList();
       List<Integer> ids = new ArrayList<>();//用來臨時存儲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(// 過濾去重
               v -> {
                   boolean flag = !ids.contains(v.getId());
                   ids.add(v.getId());
                   return flag;
               }
       ).collect(Collectors.toList());
       System.out.println(personList);

還可以實現條件過濾和列表排序：

//獲取person集合中的所有大於18周歲，並排序
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)//獲取所有18歲以上的用戶
        //.sorted(Comparator.comparing(Person::getAge))//依年紀升序排序
        .sorted(Comparator.comparing(Person::getAge).reversed())//依年紀降序排序
        .collect(Collectors.toList());
System.out.println(personList);

轉自：https://www.jianshu.com/p/63d2db850a8d