EmployeeService.java

class Employee{
    private Integer id;
    private String name;
    private Integer age;
 
    Employee(Integer id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
 
    public Integer getId() { return id; }
    public String getName() { return name; }
    public Integer getAge() { return age; }
 
    @Override
    public String toString() {
        return "Employee{ id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age + '}';
    }
}
 
public class EmployeeService {
    Map<Integer, Employee> store = Map.of(1, new Employee(1, "Peter", 34),
            2, new Employee(2, "John", 28),
            3, new Employee(3, "Bill", 42));
 
    Optional<Employee> getEmployee(Integer id){
        return Optional.ofNullable(store.get(id));
    }
}