使用Java Stream从一组集合中收集所有对象 [英] Collect all objects from a Set of Sets with Java Stream

问题描述

我正在尝试学习Java Streams并尝试从 HashSet< SortedSet< Person>> <获取 HashSet< Person> / code>。

I'm trying to learn Java Streams and trying to get a HashSet<Person> from a HashSet<SortedSet<Person>>.

HashSet<Person> students = getAllStudents();
HashSet<SortedSet<Person>> teachersForStudents = students.stream().map(Person::getTeachers).collect(Collectors.toCollection(HashSet::new));
HashSet<Person> = //combine teachers and students in one HashSet

我真正想要它将所有教师和所有教师结合起来学生在一个 HashSet< Person> 。我想在收集流时我做错了什么？

What I really want it to combine all teachers and all students in one HashSet<Person>. I guess I'm doing something wrong when I'm collecting my stream?

推荐答案

你可以 flatMap 每个学生进入由学生和他们的老师组成的小溪：

You can flatMap each student into a stream formed by the student along with their teachers:

HashSet<Person> combined = 
    students.stream()
            .flatMap(student -> Stream.concat(Stream.of(student), student.getTeachers().stream()))
            .collect(Collectors.toCollection(HashSet::new));

concat 用于连接教师的Stream，一个由学生自己组成的Stream，用 of 。

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