多级列表过滤java 8

public class Department {
    private String name;
    private List<Employee> employees;

    // 省略构造方法和其他方法
}

public class Employee {
    private String name;
    private String position;

    // 省略构造方法和其他方法
}

List<Department> departments = new ArrayList<>();
// 添加部门和员工信息到departments列表

List<Employee> filteredEmployees = departments.stream()
        .flatMap(department -> department.getEmployees().stream())
        .collect(Collectors.toList());

List<Employee> filteredEmployees = departments.stream()
        .flatMap(department -> department.getEmployees().stream())
        .filter(employee -> employee.getPosition().equals("工程师"))
        .collect(Collectors.toList());