如何在包含列表对象作为值的映射上迭代，并使用Java8 Streams将这些对象作为单独的列表对象获取

Question

有两类：

public class Company {
    
    String name;
    int regId;
    List<Employee> employee;

    //getters and setters
    //constructor
}

public class Employee {
    int id;
    String name;
    // getters and setters
    // constructor
}

对此有什么建议吗？

Answer 1

你可以做：

Map<String, Company> stringCompanyMap = new HashMap<>();
stringCompanyMap.put("Dsa", new Company("Nike", 1, Arrays.asList(
        new Employee(1, "Jordan"),
        new Employee(2, "Mike"))));
stringCompanyMap.put("Sd", new Company("Adidas", 1, Arrays.asList(
        new Employee(3, "Tyson"),
        new Employee(4, "Russel"))));

List<Employee> allEmployees = stringCompanyMap.values().stream()
        .flatMap(company -> company.employee.stream())
        .collect(Collectors.toList());

System.out.println(allEmployees);

产出：

[Employee(id=3, name=Tyson), Employee(id=4, name=Russel), Employee(id=1, name=Jordan), Employee(id=2, name=Mike)]