Java 9 Optional :: stream

There are Company and Employee classes as shown below, and there are many Employees in Company.

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

public class Company {
  private List<Employee> employees = new ArrayList<>();
  public Option<Employee> getEmployeeById(String employeeId) {
    return ->

  public List<Employee> getEmployeeList(List<String> employeeIds) {

Next, I want to get the list of ʻEmployee in the list of ʻemployeeIds, I want to implement getEmployeeList, I will implement Java8 and Java9.

public List<Employee> getEmployeeList(Collection<String> employeeIds) {

public List<Employee> getEmployeeList(Collection<String> employeeIds) {

Java 9's ʻOptional :: stream makes the code for getEmployeeList` shorter.

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