java - 如何在java 8中展平列表

Question

class Employee {
    private String name;
    private List<Employee> members;
}

List<Employee> emps = Arrays.asList(new Employee("A", Arrays.asList(
     new Employee("B", null),
     new Employee("C", null)
)))

用于展平 List 的代码:

List<Employee> total = 
    emps.stream()
        .flatMap(emp -> emp.members.stream())
        .collect(Collectors.toList());

total List应该有 3 个元素，但它只有 2 个。

Answer 1

Eran的回答是错误的，没有concat在 Stream实例。这应该有效:

emps.stream()
        .flatMap(emp -> Stream.concat(emp.members.stream(), Stream.of(emp)))
        .collect(Collectors.toList());

Stream#concat