Java Lambda Stream Distinct() 任意键 [复制]

使用Java Lambda中的Stream的distinct()方法可以根据任意键对数据进行去重操作。这个方法在处理集合中的重复元素时非常有用，它能够基于指定的键值对进行去重，并返回一个去重后的新集合。在本文中，我将介绍distinct()方法的使用方式，并给出一些实例代码来帮助读者更好地理解。

java
import java.util.Arrays;
import java.util.List;
public class DistinctExample {
    public static void main(String[] args) {
        List names = Arrays.asList("John", "Jane", "John", "Doe", "Jane");
        List distinctNames = names.stream()
                .distinct()
                .collect(Collectors.toList());
        System.out.println(distinctNames);
    }
}

[John, Jane, Doe]

java
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
class Person {
    private String name;
    private int age;
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
}
public class DistinctByKeyExample {
    public static void main(String[] args) {
        List people = Arrays.asList(
                new Person("John", 20),
                new Person("Jane", 25),
                new Person("John", 30),
                new Person("Doe", 35),
                new Person("Jane", 40)
        );
        List distinctPeople = people.stream()
                .filter(distinctByKey(Person::getName))
                .collect(Collectors.toList());
        System.out.println(distinctPeople);
    }
    public static  Predicate distinctByKey(Function keyExtractor) {
        Map seen = new ConcurrentHashMap<>();
        return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
    }
}

[Person{name='John', age=20}, Person{name='Jane', age=25}, Person{name='Doe', age=35}]