java - Apache Common MultiValueMap 迭代

Question

我有一个 MultiMap 假设 Company 以 String 作为键，另一个 MultiMap 假设 Employee 为值。 Employee Multimap 将 String 作为键，将另一个 multimap 作为值。我的问题是如何检索和迭代存储在 multimap 中的 multimap？我正在使用 Apache 通用 MultiMap。

示例:compMap 有 2 家公司。 CompA 和 CompB每个公司有 10 名员工。(员工可以多次出现，因此使用 multimap )

Coll 包含来自 compA 的员工多图，但是我如何从员工多图中检索特定员工(如果他出现 4 次)？

代码:

if (!compMap.isEmpty()){
    Set compSet = compMap.keySet( );
    Iterator compIterator = compSet.iterator();
    while( compIterator.hasNext( ) ) {
        comp= compIterator.next().toString();                                   
        Collection coll = (Collection) compMap.get(comp);
        .....  
}

Answer 1

您遇到的问题是因为一个员工不应该在一个集合中出现两次。如果您将两个值存储在 MultiValueMap 中的同一个键下，那么这些值就是不同的值(尽管它们可以通过同一个键访问)。

您应该将您的数据模型迁移到更面向对象的模型，而不是使用位于另一个 key 存储容器内的 key 存储容器( map 中的 map )。

考虑仅使用集合/列表的以下模型。值根据等于/哈希码进行区分。如果您使用列表，您可以在公司内部拥有许多员工(如果您确实需要，他们可以具有相同的名称)。为什么使用 MultiValueMap 使它复杂化？

public class AbcTest {
  public static void main(String[] args) {

    Address address1 = new Address("street1");
    Address address2 = new Address("street2");

    Employee employee1 = new Employee("employee1");
    employee1.getAddresses().add(address1);
    employee1.getAddresses().add(address2);

    Employee employee2 = new Employee("employee2");
    employee2.getAddresses().add(address2);

    Company companyA = new Company("compA");

    companyA.getEmployees().add(employee1);
    companyA.getEmployees().add(employee1); // you can add employee to the list as many times as you want, if you really need this?
    companyA.getEmployees().add(employee2);

    // now to get the employee with give name simly iterate over list of employees

    Iterator<Employee> employeeIt = companyA.getEmployees().iterator();


    Employee wantedEmployee = null;

    while (employeeIt.hasNext() && (wantedEmployee == null)) {
      Employee next = employeeIt.next();

      if (next.getName().equals("employee1")) {
        wantedEmployee = next;
      }
    }

    System.out.println(wantedEmployee);


  }



}


class Company {
  final String name;

  final List<Employee> employees;

  Company(String name) {
    this.name = name;
    this.employees = new ArrayList<>();
  }

  public String getName() {
    return name;
  }

  public List<Employee> getEmployees() {
    return employees;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if ((o == null) || (getClass() != o.getClass())) {
      return false;
    }

    Company company = (Company) o;

    if ((employees != null) ? (!employees.equals(company.employees)) : (company.employees != null)) {
      return false;
    }
    if ((name != null) ? (!name.equals(company.name)) : (company.name != null)) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    int result = (name != null) ? name.hashCode() : 0;
    result = (31 * result) + ((employees != null) ? employees.hashCode() : 0);
    return result;
  }
}

class Employee {
  final String name;
  final Set<Address> addresses;

  Employee(String name) {
    this.name = name;
    this.addresses = new HashSet<>();
  }

  public String getName() {
    return name;
  }

  public Set<Address> getAddresses() {
    return addresses;
  }

  @Override
  public String toString() {
    return "Employee{" +
      "name='" + name + '\'' +
      '}';
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if ((o == null) || (getClass() != o.getClass())) {
      return false;
    }

    Employee employee = (Employee) o;

    if ((addresses != null) ? (!addresses.equals(employee.addresses)) : (employee.addresses != null)) {
      return false;
    }
    if ((name != null) ? (!name.equals(employee.name)) : (employee.name != null)) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    int result = (name != null) ? name.hashCode() : 0;
    result = (31 * result) + ((addresses != null) ? addresses.hashCode() : 0);
    return result;
  }
}


class Address {
  final String street;

  Address(String street) {
    this.street = street;
  }

  public String getStreet() {
    return street;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if ((o == null) || (getClass() != o.getClass())) {
      return false;
    }

    Address address = (Address) o;

    if ((street != null) ? (!street.equals(address.street)) : (address.street != null)) {
      return false;
    }

    return true;
  }

  @Override
  public int hashCode() {
    return (street != null) ? street.hashCode() : 0;
  }
}