RestController
@RequestMapping("/employees")
public class EmployeeController {
    private List<Employee> employeeList;
    public static List<Integer> employees;
    private Map<Integer, Employee> employeeMap;

    public EmployeeController() {
        this.employeeList = new ArrayList<>();
        this.employeeMap = new HashMap<>();
        employees = new ArrayList<>();
    }

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

    @PostMapping("/{id}/add/{projectId}")
    public String addEmployee(@PathVariable int projectId, @PathVariable int id) {
        if (!employeeMap.containsKey(id)) {
            throw new ResponseStatusException(HttpStatus.NOT_FOUND, "Employee with this id not found");
        }
        if (employeeList.get(id).getProjectList().contains(projectId)) {
            throw new ResponseStatusException(HttpStatus.IM_USED, "This project is already added");
        }
        if (!ProjectController.getProjects().contains(projectId)) {
            throw new ResponseStatusException(HttpStatus.NOT_FOUND, "This project is not created");
        }
        employeeMap.get(id).setProjectList(projectId);
        return String.format("Project was added to employee tasks");
    }