java - 不使用flatMap实现flatMap效果

Question

我有一个定义开发人员的类。

class Developer {
    private final String name;
    Set<String> skills = new HashSet<>();

    public Developer(final String name, final String... skills) {
        this.name = name;
        for (final String skill : skills) {
            this.skills.add(skill);
        }
    }
}

我正在创建一个开发人员列表。

List<Developer> developers = new ArrayList<>();
people.add(new Developer("Bill", "Javascript", "HTML", "CSS"));
people.add(new Developer("Bob", "Java", "OOP", "Agile"));
people.add(new Developer("Barry", "Data Mining", "Machine Learning", "R"));

现在我想提取一套集体技能。我使用 flatMap 执行此操作，如下所示:

 Set<String> skills = developers.stream().flatMap(dev -> dev.skills.stream()).collect(Collectors.toSet());

有没有办法通过Stream来做到这一点而不使用flatMap？

Answer 1

编辑

无需在收集器内使用线程安全结构，因为 the documentation说:

When executed in parallel, multiple intermediate results may be instantiated, populated, and merged so as to maintain isolation of mutable data structures. Therefore, even when executed in parallel with non-thread-safe data structures (such as ArrayList), no additional synchronization is needed for a parallel reduction.

<小时/>

flatMap 是正确的选择。很高兴知道您问题背后的动机。

实现相同结果的另一种方法是使用 collectors (如其他答案所述)。您还可以避免使用 map 并将所有内容放入收集器中，例如:

Set<String> skills = developers.stream()
    .collect(
        HashSet<String>::new, 
        (acum, dev) -> acum.addAll(dev.skills), 
        Set::addAll
    );