我对这段代码有一个问题，我完全按照视频教程（我正在学习）的方法来做，但是它不起作用，需要一些声明。有可能指南中的代码是用一些旧的方法编写的？它是没有服务的硬代码。
app-routing.module.ts

import { NgModule } from '@angular/core';
import { Routes, RouterModule } from '@angular/router';
import { DepartmentListComponent } from './department-list/department-list.component';
import { EmployeeListComponent } from './employee-list/employee-list.component';

const routes: Routes = [
  { path: 'departments', component: DepartmentListComponent },
  { path: 'employees', component: EmployeeListComponent }

];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }
export const routingComponents  [DepartmentListComponent, EmployeeListComponent ]

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import { AppRoutingModule, routingComponents } from './app-routing.module';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent,
    routingComponents
  ],
  imports: [
    BrowserModule,
    AppRoutingModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.component.html

<h1> Welocme in routing</h1>

<router-outlet></router-outlet>

我需要看到运行应用程序与改变网址形式http://localhost:4200/employees和http://localhost:4200/departments。我是乞丐，所以请理解。